Illustrator: How to trim lines in a circle?

Question

im working on a little analyses drawing but im stuck with trimming some lines. Im drawing infrastructure with a circle over it to specify a location of intrest. But i need to cut the lines (drawn with the pen tool) to the contour of the circle. (i know its weird what im saying lol, please look at the pictures). Im using pathfinder tool and it worked the first time (see picture) but now it wont.

Am i doing it wrong?

Picture 1 is what i need to do, the circle cutting of the paths so its only colored in the circle

Picture 2 is what i need to cut

picture 3 is the message i get

Sorry for bad English, its not my native language ;)

Answer 1

I think you can do this with the Shape Builder Tool (Shift+M).

Just select all the paths, then while holding down Alt click + drag on the path areas you want to delete.

This will leave you with the remaining paths within the circle.

---

Another idea is to bring the circle to the top and select all and create a clipping mask (Ctrl+7). This will crop out everything non destructively - still allowing you to easily edit.

If you want to show the actual circle stroke. Make sure to clone it first, as the clipping path is not going to be visible.