I am doing with the inbuilt tutorial of solidworks and I in a fix. In ADVANCED DESIGN TECHINEQUES we have to make a hinge.

In that there is a topic called COMPLETEING THE FIRST SET OF HINGE CUTS. I am not able to perform the extrude cut that is involved in that step. In fact I cant even understand what on what entity we are performing that extrude cut operation. It is not working for me. Can anyone please help? I have been toiling for 2 days now.