BW Sparky

My stapler jammed and manged to free it up after taking most of it to bits, the problem I have is trying to get the cartridge holder put back together? there is a bracket that I guess sits on the cartridge track but there is an almost small key looing piece of metal with a screw hole through it, I've tried so many ways to try and fix it onto the sliding bracket but non of it appears to work? does anyone have a any ideas or advice please? Thanks