AutoCAD OSNAP, Ortho & Polar Tracking: Draw with 100% Accuracy (2026)

Here is a mistake almost every beginner makes: you click “on” the end of a line, the drawing looks perfect, and everything seems fine. Then you try to hatch a room and AutoCAD says it cannot find a closed boundary. Or your slab area comes out wrong by a few square centimetres. The reason is a tiny gap you cannot see.

We touched on this in our AutoCAD interface guide: without OSNAP, lines leave tiny gaps. In this lesson you will learn how to fix that for good using three tools, OSNAP, Ortho and Polar Tracking, with the exact settings we recommend for civil drawings.

Quick answer: what is OSNAP in AutoCAD?

OSNAP (Object Snap) pulls your cursor to exact points on existing objects, such as the endpoint of a line, the midpoint of a wall or the centre of a circle. Press F3 to turn it on or off. It is the main tool that removes gaps and guesswork from your drawing.

This is Lesson 2 of our free AutoCAD for Civil Engineers series. If you have not done it yet, start with Lesson 1: AutoCAD Layers Explained, because we will use the same layers here.

THE CIVIL STUDIES · FREE TOOL

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Why Accuracy Matters in Civil Drawings

In civil engineering, a drawing is not a picture. People take measurements, areas and quantities from it. A gap of even 0.5 mm in the drawing can:

• Break hatching: AutoCAD cannot fill an area that is not fully closed.
• Give wrong areas: plot area, floor area and slab area come out incorrect.
• Stop TRIM, FILLET and EXTEND from working properly.
• Cause wrong quantities: road length, wall length and boundary lengths do not add up.
• Waste time: someone has to hunt for the gap, often hours later.

The 6 Function Keys You Must Know

These keys sit on the status bar as buttons too. Memorise them and you will draw much faster.

Key	Tool	What it does	Keep it on?
F3	OSNAP	Snaps your cursor to exact points on objects	Yes, always
F8	Ortho	Locks lines to 0° and 90°	Yes, for walls and grids
F10	Polar Tracking	Shows guide lines at set angles (30°, 45°, etc.)	Yes, for angled work (turns Ortho off)
F11	Object Snap Tracking	Tracks lines out from snap points to align objects	Yes, with OSNAP on
F12	Dynamic Input	Shows length and angle boxes near the cursor	Personal choice
F9	Snap (grid snap)	Forces the cursor to jump in fixed steps	No, keep it off for civil work

Beginner trap: F9 (Snap) and F3 (OSNAP) are different. F9 makes the cursor jump in a grid, which is useless when your dimensions are 230 mm or 3.65 m. Keep F9 off. OSNAP (F3) is the one you want.

OSNAP Explained: Running vs One-Time Snaps

According to Autodesk’s official help on object snaps, you can use them at any time AutoCAD asks you for a point. There are two ways to use them:

1. Running OSNAP (always on)

These stay active for every command until you turn them off. You choose which modes are on, and press F3 to switch them on or off. This is what you will use 95% of the time.

How to set them: right-click the OSNAP button on the status bar, pick Object Snap Settings (or type OSNAP), tick the modes you want and click OK.

2. One-time snap override

You apply a snap for only the next point you pick. Hold Shift and right-click to open the snap menu, or type the short code in the middle of a command (for example MID). After that one point, AutoCAD goes back to your running snaps.

Useful trick: when several snaps sit close together, press Tab to cycle through the options before you click.

OSNAP Modes and Where to Use Them

When you hover over an object, a small coloured marker shows which snap is active. This is called AutoSnap.

Mode	Type it as	Marker	Civil use example
Endpoint	END	Square	Join wall corners, road edges, plot boundaries
Midpoint	MID	Triangle	Centre of a wall, window or door opening
Center	CEN	Circle	Centre of a circular column, manhole or tank
Intersection	INT	X	Grid line crossings, where a beam meets a column
Perpendicular	PER	Right-angle symbol	Shortest line from a point to a road edge or boundary
Extension	EXT	Dotted line with +	Continue an edge in line with an existing one
Tangent	TAN	Circle with a tangent line	Road curves, fillets, pipe bends
Quadrant	QUA	Diamond	Top, bottom, left, right points of a circle
Node	NOD	Circle with X	Survey points and point objects
Insertion	INS	Square within a square	Insertion point of blocks and text
Parallel	PAR	Two short parallel lines	Draw a line parallel to an existing sloping line
Nearest	NEA	Hourglass	Avoid as a running snap. It is not exact

Best OSNAP Settings for Civil Engineers

Do not tick everything. Too many running snaps make the cursor jump to the wrong point in a crowded drawing. For civil work we recommend keeping these six on:

• Endpoint
• Midpoint
• Center
• Intersection
• Perpendicular
• Extension

Use Tangent, Quadrant, Node and Parallel as one-time overrides, only when you need them. Keep Nearest off, because it lets you click anywhere on a line and can bring the gaps right back.

Set your snaps with one command (bonus AutoLISP)

Save this in Notepad as snapset.lsp, load it with APPLOAD, then type SNAPSET in any drawing. It sets the six recommended snaps in one go.

(defun c:SNAPSET ()
  ;; Endpoint 1 + Midpoint 2 + Center 4 + Intersection 32 + Perpendicular 128 + Extension 4096
  (setvar "OSMODE" 4263)
  (princ "\nRunning OSNAP set: END, MID, CEN, INT, PER, EXT.")
  (princ)
)

Want a different set? OSNAP modes are stored as numbers. Add the ones you want: Endpoint 1, Midpoint 2, Center 4, Node 8, Quadrant 16, Intersection 32, Insertion 64, Perpendicular 128, Tangent 256, Nearest 512, Extension 4096, Parallel 8192.

Quick Setup: Layers and Snaps in 2 Minutes

Accuracy starts before you draw the first line. If your layers are wrong and your snaps are off, your drawing will be messy no matter how careful you are. Here is the fast way to start every new drawing:

Once your layers are ready, save everything into a .dwt template as shown in Lesson 1, so every new drawing starts clean.

Object Snap Tracking (F11): Align Without Drawing Extra Lines

Object Snap Tracking lets you line up new points with existing points without drawing any construction lines. It only works when OSNAP (F3) is on.

How it works:

1. Start a command, for example LINE.
2. Hover over a snap point, such as an endpoint or midpoint, until a small + appears. Do not click.
3. Move the cursor away. A dotted tracking line stretches out from that point.
4. Hover over a second point to get a second tracking line. Where the two lines cross, click. That point is aligned with both.

Where you will use it:

• Place a window exactly in the centre of a wall (track from the midpoint of the wall).
• Align a column in the upper floor plan with the column below it.
• Line up a door with the centre of a room without drawing a helper line.

Ortho Mode (F8): Perfect Horizontal and Vertical Lines

Ortho forces your cursor to move only straight up, down, left or right. It is perfect for walls, road grids and boundaries.

The best way to use it is with Direct Distance Entry, the fastest drawing method in AutoCAD:

1. Turn Ortho on with F8.
2. Type L and press Enter to start a line, then click the start point.
3. Move the cursor in the direction you want, for example to the right.
4. Type the length, for example 3650, and press Enter.
5. Move up, type 3000, Enter. Keep going, then press C to close the shape.

Quick tip: Hold Shift to switch Ortho temporarily. If Ortho is on, Shift turns it off while held. If it is off, Shift turns it on while held. With Direct Distance Entry you never need to type coordinates, only the length.

Polar Tracking (F10): Accurate Angles Without Typing

Polar Tracking shows a dotted guide and a tooltip when your cursor gets close to a set angle. It is Ortho’s smarter cousin: it works at 90° but also at 45°, 30°, 15° or any angle you choose.

How to set polar angles

1. Right-click the Polar Tracking button on the status bar and pick a ready angle such as 90, 45, 30 or 15, or pick Tracking Settings for full control.
2. In the Polar Tracking tab, choose an Increment angle.
3. Tick Additional angles and click New to add special angles that are not multiples of your increment.
4. Click OK, press F10 to turn it on, and draw with Direct Distance Entry just like Ortho.

Civil examples of additional angles

• Ramp at 1:12 slope: add 4.76 degrees (the angle whose rise over run is 1 in 12).
• Staircase pitch: use an increment of 30 for a 30° stair line.
• Roof slope drawings and sloping boundaries: add the angle you need once, then track to it every time.

Tip: The settings also let you measure polar angles “Relative to last segment”. This is helpful when you draw a road alignment, because the angle you see is the deflection from the previous line.

Ortho vs Polar Tracking: Which One Should You Use?

Feature	Ortho (F8)	Polar Tracking (F10)
Angles	Only 0° and 90°	Any increment you set, plus custom angles
Cursor behaviour	Locks strictly to horizontal or vertical	Shows a guide line when close to the angle
Best for	Walls, column grids, plot boundaries	Sloped roads, ramps, stairs, angled boundaries
Use with OSNAP?	Yes	Yes
Both on together?	No. Turning one on turns the other off.

Simple rule: if your drawing is mostly right angles, use Ortho. If it has angles, use Polar Tracking set to 90° plus your extra angles. That gives you Ortho behaviour and more.

How to Check Your Drawing for Gaps

Even experienced drafters inherit drawings with gaps. Use these three quick tests:

1. Join test: type PEDIT, choose Multiple, select all the lines of a room or boundary, then choose Join. If they turn into one closed polyline, there are no gaps. If not, a gap exists.
2. Hatch test: pick a point inside the area with HATCH. If AutoCAD says it cannot find a closed boundary, there is a gap or overlap.
3. Zoom test: zoom in heavily on corners you suspect. If you see a break or overshoot, fix it with FILLET using radius 0, or redraw with OSNAP.

Common Problems and Fixes

Problem	Likely cause	Fix
Snap markers do not appear	OSNAP is off, or no modes are ticked	Press F3. Check the modes in Object Snap Settings
Cursor jumps to the wrong point	Too many running snaps in a crowded area	Keep only the six recommended modes. Press Tab to cycle
Cannot snap to an object	Its layer is off or frozen	Turn the layer on or thaw it. (Locked layers still allow snapping)
Cannot snap to a hatch	Hatch objects are ignored by default	Set the OSNAPHATCH system variable to 1
Cursor moves in fixed steps	Grid Snap (F9) is on	Press F9 to turn it off
Cannot draw at an angle	Ortho (F8) is on	Turn it off, or use Polar Tracking (F10)
Polar guide does not appear at your angle	Angle is not in your increment or additional angles	Add it under Additional angles in Tracking Settings
Snaps feel shaky or inaccurate on a survey drawing	Objects are very far from the origin (very large coordinates)	Move the drawing closer to 0,0 (keep a note of the shift) or work with a local coordinate system
Extension snap does not work	Extension is off, or the cursor did not pause on the endpoint	Tick Extension. Hover on the endpoint first, then move along the dotted line

10-Minute Practice Exercise: Plot, Setback and Driveway

Do this in a new drawing with units in millimetres (1000 units = 1 metre). Use the layers from Lesson 1, or generate them fast with the Layer LISP Generator.

1. Set up: turn on OSNAP (F3) with Endpoint, Midpoint, Intersection and Perpendicular, and turn on Ortho (F8).
2. Plot boundary: make C-SITE-BNDY current. Type L, click a start point, move right and type 20000, up 15000, left 20000, then type C to close. That is a 20 m × 15 m plot.
3. Setback: type OFFSET, enter 3000, click a boundary line and then click inside. Repeat for all four sides. Trim the corners with FILLET radius 0, and move the new lines to A-WALL using LAYMCH. You now have a 14 m × 9 m building footprint.
4. Driveway centreline: make C-ROAD-CL current. Start a LINE at the midpoint of the building’s front wall (hover until the triangle appears). For the second point, type PER, then click the plot boundary’s front edge. The line runs perfectly square to the boundary.
5. Object Snap Tracking: turn on F11. Draw a small 1000 mm door opening in the centre of the back wall. Hover over the wall’s midpoint, move along the tracking line, and use Direct Distance Entry to place each end 500 mm from the centre.
6. Polar angle: open Tracking Settings, add the additional angle 4.76, turn on Polar Tracking (F10), and draw a 6000 mm line at that angle. This is a 1:12 ramp. Type LIST and pick it to check the angle.
7. Gap test: use PEDIT > Multiple > Join on the four building lines. If they turn into one closed shape, your snapping was perfect.

Key takeaways

• F3 OSNAP for exact points, F8 Ortho for straight lines, F10 Polar for angles, F11 tracking for alignment. Keep F9 off.
• Use only six running snaps: Endpoint, Midpoint, Center, Intersection, Perpendicular and Extension. Keep Nearest off.
• Draw with Direct Distance Entry: move the cursor, type the length, press Enter.
• Ortho and Polar cannot run together. Use Polar with 90° plus extra angles for mixed drawings.
• Test for gaps with PEDIT Join or a hatch test before you send any drawing.
• Save time on every project with your layers ready through the Layer LISP Generator and your snaps ready through SNAPSET.

AutoCAD OSNAP, Ortho and Polar Tracking FAQs

What is OSNAP in AutoCAD?

OSNAP, short for Object Snap, makes the cursor snap to exact geometric points on objects such as endpoints, midpoints, centres and intersections. It lets you draw and edit with exact accuracy instead of clicking near a point.

What is the shortcut key for OSNAP in AutoCAD?

Press F3 to turn running object snaps on or off. You can also click the OSNAP button on the status bar. Your chosen snap modes are remembered when you turn it off, so they return when you turn it back on.

What is the difference between Ortho and Polar Tracking?

Ortho locks the cursor to horizontal and vertical directions only. Polar Tracking shows guide lines at any angle increment you set, such as 30 or 45 degrees, plus custom angles. Use Ortho for right-angle work and Polar for angled work.

Can I use Ortho and Polar Tracking at the same time?

No. Turning on Ortho automatically turns off Polar Tracking, and turning on Polar Tracking turns off Ortho. If you need both, set Polar Tracking to 90 degrees and add the other angles you need.

Which OSNAP modes should I keep on for civil drafting?

Keep Endpoint, Midpoint, Center, Intersection, Perpendicular and Extension on as running snaps. Use Tangent, Quadrant, Node and Parallel only as one-time overrides, and keep Nearest off because it is not exact.

Why is OSNAP not working in AutoCAD?

Most often OSNAP is switched off with F3, no snap modes are ticked in Object Snap Settings, or the object is on an off or frozen layer. Hatch objects are also ignored unless the OSNAPHATCH system variable is set to 1.

What is Object Snap Tracking in AutoCAD?

Object Snap Tracking, turned on with F11, shows temporary alignment lines from snap points you hover over. It helps you place points in line with existing objects, such as the centre of a wall, without drawing extra construction lines. OSNAP must be on for it to work.

Why does my cursor keep snapping to the wrong point?

Usually too many running snap modes are on in a crowded area, so AutoCAD picks the nearest one. Reduce your running snaps to the six recommended modes, zoom in, or press Tab to cycle through the available snap points before you click.

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AutoCAD for Civil Engineers: Complete Course

You are on Lesson 2 of 6. Previous: Lesson 1: AutoCAD Layers Explained. Next up: Dimensioning and Text Styles for civil drawings.

More from this series and tools:

• AutoCAD Layer LISP Generator (create layers fast)
• AutoCAD for Civil Engineers: The Complete Beginner’s Guide
• AutoCAD Interface Explained: Labeled Diagram, All Parts & Functions
• Essential AutoCAD 2D Commands for Beginners