Preheat the oven to 350 F and place a rack in the center of the oven.
Blend the graham crackers in a blender until they become a fine powder, similar to flour. You really want the graham crackers to be fine. If they are too coarse, the crust will be too porous causing the custard to soak into it.
In a medium bowl stir together the sugar, salt, and ground graham crackers. Pour in the melted butter and vanilla and use a fork to mix everything together.
If it's too dry add a little more butter but be careful not to make it too wet. It should still seem crumbly.
Pour the mixture into the tart pan. Press most of the crust into the sides of the pan first and then the rest across the bottom with your fingers.
Use your thumb or your pointer finger to really press it into the bottom corner so that you don't get a super thick pastry corner. Make sure the crust reaches all the way to the top of the pan.
Take your time with this, it's important that it is neat and even before baking and filling. I like to go in with a flat bottomed cup to press the crust in cleanly after I've done 95% with my fingers.
Place the pan on a baking sheet and then bake it in the hot oven for 12-15 minutes until it looks dry on the surface.
Set the crust aside to cool down, be careful not to bump or touch it as it is extra fragile while warm.