Hi niko, also one other note - Trim actually has a projection method built into it already so it is not necessary to do the projection as an extra step.

So for example you have this surface and this curve:



Select the surface, run Trim, and then select the curve as the cutting object. Then right-click or press Done to keep all the cut up pieces. That will leave you with this result:



Select that small face, and then run Extrude:



- Michael