Intersect

Keeps only the material that lies inside a region and removes the rest. The region is one side of a plane, a box you type, or another body.

When to Use It

Keep one half of a part: everything above the Top plane, or behind a face
Trim a part down to a box, for example to keep only the corner you are working on
Shape several bodies with one body: each keeps only what it shares with that body

Click Advanced on the Features tab, then Intersect. Modeling must be open (it comes with the Pro plans).

Keep the material inside: the region.
One side of a plane: keeps what is on the side the plane faces: above Top plane, in front of Front plane, right of Right plane, behind a picked flat face (inside the part). Choose the plane the same way as in Split: Top, Front, Right, Sketch plane, a Reference plane, or Pick a flat face. Tick Flip side to keep the other side.
A box: type the From corner (X, Y, Z) and the To corner (X, Y, Z) in any unit. Fit to the part fills in the box around the whole part, so you only change the sides you want to trim.
A body: choose the Body whose shape is kept. Every other body keeps only what it shares with it, and that body is used up.
Bodies to trim: tick the bodies to trim. With none ticked, every body is trimmed (with A body, every other body).

A line under the list says what will happen.

Click Advanced on the Features tab, then Intersect.
Choose One side of a plane, A box or A body.
Choose the plane (and Flip side if needed), type the box corners, or choose the body.
Tick the bodies to trim, or leave them all unticked.
Press Intersect. The result is one step in History, and the toast says the new volume.

Each body keeps its name and only the material inside the region. A 10 mm cube kept above a plane 3 mm up its side keeps 700 mm³.
If the region cuts a body into separate pieces, each extra piece becomes a body of its own with the next free name.
A body with no material inside the region is removed. The toast names every body removed this way.
With A body, the body whose shape is kept is used up, the way Combine uses up its bodies. To keep only the overlap of bodies as ONE body, use Combine with Common instead.

Intersect is refused in plain words, and the part is left as it was, when:
nothing of the part lies inside the region, so no body would be left
all of the part already lies inside the region, so nothing would be removed
the box is flat (From and To are the same in X, Y or Z), a size is not a number, or a size is over 10,000 metres
there is no other body for A body, or the body whose shape is kept is also ticked to trim
the result would not be sound bodies, or would come to more than 400 bodies in all
Intersect is a History step like any other: Undo takes it back, and in the Model tree you can suppress it, delete it or drag it to another place. To change the region, delete the step and make it again.
The bodies are remembered by their exact size and place. If an earlier step changes one of them, this step stops and names the body rather than trim a different one. With no body ticked, the step trims whatever bodies the part has when it is rebuilt, so a body an earlier step adds later is trimmed too (or removed, when nothing of it is inside).
A model with an Intersect step stops at that step when it is opened in an older viewer that does not have Intersect.

Nothing of the part lies inside: the region is on the wrong side or misses the part. Tick Flip side, or make the box overlap the part.
Nothing would be removed: the whole part is already inside the region. Pick a plane that crosses the part, or make the box smaller.

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