If you're serving a pie with a graham cracker crust, don't worry if a crack appears here or there. Only worry about repairing ones that threaten to make the pie collapse when you cut it. It's best to prevent cracks from forming instead of trying to fix them afterward. Do this by coating the pie pan with nonstick cooking spray before pressing the crust into it to hold the graham crackers together and make it easier to slice the pie.
Set a few tablespoons of graham cracker crumbs aside after pressing the crust into the pan. If cracks appear in the crust after it's baked, press some of the leftover crumbs into them before adding the pie filling. These help hold the pie together, and no one will notice the few pieces of crumbs that aren't baked.
Spread some honey or maple syrup evenly over the cracks with a knife, and let it congeal before adding the filling. The sweet flavor of the syrup or honey blends in with the pie's taste without disrupting the flavor.
Mix 1 tsp. sugar with 1 melted tsp. butter, and press the mixture against the cracks to seal them. Let it cool before pouring the filling into the pie pan. This works in a pinch if you don't have any more graham crackers available.