tighten sight on Glenfield 30A

What is the best way to tighten the rear open sight on a Glenfield M30A, the Marlin made 30-30? It wiggles back and forth and appears to be simply crimped in position. Therefore, I assume that it needs to be pinched tight again. Just need to know the right tool, etc., so as not to do more damage than good. Thanks.