AutoCAD TH Shortcut : THICKNESS : Sets the default 3D thickness property when creating 2D geometric objects

If you need to give 2D objects a uniform third‑dimension look in AutoCAD, the thickness shortcut is a quick way to do it. This guide explains what the shortcut does, how to use it step by step, why it may fail, alternative methods to get 3D geometry, practical examples, troubleshooting, and time‑saving tips.

What is the thickness shortcut?

The thickness property in AutoCAD sets a uniform Z axis value (height) for 2D objects such as lines, polylines, circles, arcs, and rectangles, effectively giving them a simple 3D appearance by offsetting their geometry along the Z axis. The thickness is not a solid extrusion — it is a per‑object property that adds depth to 2D entities.

Common names and controls:

• The command/shortcut can be typed as THICKNESS or the alias TH at the command line.
• You can also view or change thickness in the Properties palette (press Ctrl+1).
• To produce true 3D solids, use EXTRUDE, PRESSPULL, or convert regions to solids.

Important behaviors:

• Thickness applies to new objects created after the thickness value is set, unless you manually change an existing object’s thickness.
• A positive thickness extends geometry in the positive Z direction; a negative value extends in the negative Z direction.
• In a Top view with a 2D visual style, thickness may not be visually obvious — switch to an isometric or 3D visual style to see depth.

How to use the thickness shortcut (Step by step)

Follow these steps to set and apply thickness correctly:

1. Open your drawing and ensure the correct UCS (User Coordinate system) is active for the orientation you want.

2. Set the thickness value:

   • Type TH or THICKNESS at the command line and press Enter.
   • When prompted, enter the desired numeric value (for example 10 or -5) and press Enter.
   • The value you enter becomes the default thickness for subsequently created objects.

3. Draw objects after setting thickness:

   • Use LINE, CIRCLE, RECTANGLE, PLINE (Polyline), etc. Any new 2D entity will inherit the thickness value.
   • Example: set TH = 10 then draw a rectangle; the rectangle will have a thickness of 10 along Z.

4. View the thickness:

   • Switch to an isometric view (e.g., SE ISOMETRIC or use the ViewCube).
   • Change visual style to 3D Wireframe or Shaded to see thickness.
   • If you don’t see changes, run REGEN and verify UCS orientation.

5. Modify thickness of existing objects:

   • Select the object, open the Properties palette (Ctrl+1), find the Thickness field and enter the new value.
   • Or use MATCHPROP to copy thickness from one object to another.

Notes:

• Thickness is stored per object; changing the global thickness later does not retroactively change objects you already created unless you edit them individually.
• For negative thickness, objects extend below the current plane; useful for cutouts or recessed features.

Practical examples

Example 1 — Quick pseudo‑3D rectangle:

• Type TH → Enter 8.
• Use RECTANGLE to draw a rectangle.
• Switch to SE Isometric and 3D Wireframe to view the depth.

Example 2 — Adjust thickness for an existing polyline:

• Select the polyline → press Ctrl+1 → set Thickness to -5.
• The polyline now extends 5 units below the drawing plane.

Example 3 — When you need a solid rather than thickness:

• Draw a closed polyline or region.
• Use EXTRUDE and enter height 8 to get a true 3D solid (better for modeling and Boolean operations).

Alternative methods to produce depth or solids

When thickness is not appropriate, use these alternatives:

• EXTRUDE: Converts a closed 2D shape (region, polyline) into a 3D solid with controllable height and direction. Use for precise solid modeling and Boolean operations.
• PRESSPULL: Click inside a closed boundary and pull to create a 3D solid quickly; handles complex boundaries.
• SWEEP: Sweep a profile along a path to create varied 3D geometry.
• REGION + EXTRUDE: Convert closed curves to a REGION then extrude to form a solid (better for some operations).
• 3D modeling Workspace / Solid Tools: Use the modeling toolset for fillets, unions, subtractions, etc.

Use thickness for quick, lightweight pseudo‑3D visuals and drafting where a true solid is not required.

Why the thickness shortcut sometimes doesn’t work (errors and fixes)

Common issue: You set thickness but newly drawn objects appear flat.

• Fixes:
  • Ensure you are not in the Top view with a 2D visual style; switch to isometric and 3D Wireframe or Shaded.
  • Run REGEN to refresh the drawing.

Common issue: Changing thickness has no effect on selected objects.

• Causes and fixes:
  • The object may be a 3D solid already — thickness property does not apply to solids. Use EXTRUDE/EDIT instead.
  • The object might be part of a block or an Xref — explode the block or edit the block definition, or edit the Xref.
  • The object type doesn’t support thickness (e.g., HATCH or specialized objects) — convert to region or boundary if necessary.

Common issue: Thickness applies only to new objects, not existing ones.

• Fix: Select existing objects and update their Thickness in Properties (Ctrl+1) or use MATCHPROP.

Common issue: Thickness set but the direction is inverted or not visible.

• Fixes:
  • Use negative values for thickness to extend below the current plane.
  • Verify the UCS and make sure the Z axis is aligned as expected.

Permission or settings issues:

• Some CAD standards or custom LISP routines may reset thickness — check startup scripts or CAD standards in your company template.

Tips and best practices

• To set thickness quickly from the keyboard, use the alias TH and enter numeric values.
• Use Ctrl+1 to toggle the Properties palette for fast object inspection and editing.
• If you need objects to participate in 3D operations (unions, subtractions), prefer regions + EXTRUDE to thickness.
• Use negative thickness deliberately when you want geometry to go below the drawing plane.
• For presentation drawings where performance matters, thickness gives a fast 3D impression without creating heavy solids.
• Save a template with common thickness defaults for repetitive tasks to speed up drawing setup.
• When scripting or using LISP, remember that thickness is a drawable property and can be set programmatically for batches of objects.

FAQ

How do I know whether to use thickness or extrude?

Use thickness for quick pseudo‑3D visual depth on 2D geometry (lightweight). Use EXTRUDE when you need real 3D solids for modeling, Boolean operations, or accurate volume calculations.

Will thickness affect printing or plotting?

Thickness affects geometry in Model space and will be visible in views that display 3D depth. For 2D plot styles (Top view, flat visual style), thickness may not show. Use viewports or 3D visual styles to control printed appearance.

Can I apply thickness to many objects at once?

Yes — select multiple compatible 2D objects, open Properties (Ctrl+1), and set Thickness. You can also use MATCHPROP to copy thickness from one object to many.

Why can’t I change thickness on a block or Xref?

Blocks and Xrefs are external or grouped definitions. To change thickness, edit the block definition or explode it (if appropriate), or edit the source drawing for the Xref.

Does thickness affect Object snap or drawing coordinates?

Thickness adds a Z value to object coordinates; most 2D snaps still work but some tools that expect flat geometry may behave differently. For precise 3D snaps, enable 3D SNAP or adjust the UCS as needed.

How do I remove thickness from an object?

Select the object, open Properties (Ctrl+1), and set Thickness to 0. If the object was converted to a solid, use appropriate 3D edit tools instead.

Is there an automatic way to convert thicknessed objects into solids?

Not directly; to get solids, recreate or convert 2D boundaries into REGION, then use EXTRUDE, or use PRESSPULL to generate solids from closed areas.