Extrude and Cut
Use Extrude to give the closed areas of a sketch a third dimension. Select one or more regions, type a distance, and choose what the result does to the bodies already there. The same tool with Combine set to Subtract is how you take material away again.
What it consumes: regions, not lines
An extrude consumes regions: the closed areas a sketch splits itself into. Regions and Profiles covers how a sketch becomes them. Pick one, pick several, or turn on All regions and let the sketch decide.
The switch matters more than it looks. Pick regions by hand and the feature holds on to those specific areas, so a circle you draw somewhere else in the sketch later is ignored. A circle you draw inside a picked region is not: any region you did not pick that sits inside one you did is cut out on every rebuild, so it arrives as a hole. Turn All regions on and the feature re-reads the sketch every time it rebuilds, so anything you draw later is swept in automatically.
A region you select is always filled. Holes come from the regions you leave out.
Which way, and how far
| Setting | What you get |
|---|---|
| One direction | One prism, growing from the sketch plane |
| Symmetric | The distance split evenly about the plane, half each side, as one solid rather than two glued together |
| Two directions | A distance forward and a different one back, each its own field |
Distance takes anything a dimension takes: a number, a parameter, an expression. Keep it up to 500 mm, and note that it cannot be zero.
One rule decides which way is forward. A sketch on a world plane always grows along its normal. A sketch on anything else, meaning a face of the model or a reference plane, grows along the normal when you are adding or making a new body, and into the material when you are subtracting. A cut sketched on a face therefore does the obvious thing without you flipping anything.
New body, add, or subtract
| Mode | What happens |
|---|---|
| New body | The prism becomes a body of its own, touching nothing |
| Add | It joins the bodies listed in the Fuses with row. Nothing to join? You get a new body |
| Subtract | It is removed from one body you name |
The two are not symmetric. Subtract asks you to name the body to cut, so pick it before you confirm. Add answers that question for you, and then shows you the answer: a Fuses with row names the bodies the prism welds itself onto.
That row is live while you are still drawing the step. Drag the height onto a neighbour and the neighbour joins the list; hide a body and it drops out of it, because while a step is being drawn only visible bodies are candidates. The moment you click into the row and pick bodies yourself, the list is yours and nothing re-answers it over you. Closing the popover freezes whatever was written last, and from then on the extrude joins exactly those bodies and nothing else: a body that arrives later stays out, and a body on the list that has since gone stops the step rather than quietly welding somewhere else.
A subtract that cuts the body in two gives you two bodies. Take the middle out of a bar and what is left is no longer one connected solid, so the pieces are handed back separately. The biggest piece by volume stays the body you were cutting, with its name, its colour and its visibility; the rest arrive as “Bar (2)”, “Bar (3)” and so on, keep any rename or recolour you give them, and disappear again if you delete the cut.
Where it goes in the timeline
Creating an extrude hides the sketch it consumed. The sketch is not gone. It is a step in the timeline like any other, so re-open the sketch to change the shape, and open the extrude to change the numbers: distance, direction, and what it combines with.
With the popover open, ↵ confirms the step and Esc cancels it. On a step you have just made, cancelling removes it; on one you were editing, it puts the step back exactly as it was when you opened it and files no undo entry, so the next undo reaches whatever you did before the edit rather than the edit itself.
See also
- Where an Extrude Stops: where the prism stops and where it starts
- Regions and Profiles: what it consumes
- Union and Intersect: joining bodies that already exist
- Cut and Push Face: removing material without a sketch