Blind baking is baking an unfilled pie shell to produce a partially- or fully-baked crust. Blind baking the crust prevents the crust from becoming soggy from custard based fillings, and is necessary for pies which have the fillings either cooked separately or not at all.
To blind bake a crust, once your crust is prepared and placed in your pie pan, prick a few holes (this is called "docking") or fill it with pie weights (do one or the other, if you fill it with weights, you don't need to dock), and bake until browned (or just for several minutes if your goal is a partially-baked crust).
To fully blind bake, bake it at 425 degrees 15 to 18 minutes or until the sides begin to brown. (The initial high heat will force much of the steam out, helping the crust become flaky.) Remove the pan from the oven. Gently remove your pie weights. Reduce oven to 375 degrees and continue to bake the crust for several minutes until it's golden.
Without the weight of a filling, a baking crust can shrink, fill with air pockets, and puff up with bubbles, so it is important to either dock the crust or weigh the crust down as it bakes. Weights are easier and you won't risk the filling leaking through the holes. This is done by lining the dough with parchment paper or foil (if you use foil, you may need to grease the dough first, to prevent the foil from sticking) and filling it with pie weights or a pie chain (or dried beans, pennies, rice, marbles, etc.) to hold its shape during baking. [TIP: Keep your weights in an oven cooking bag. You can just place the bag with the weights in the pie crust, then lift the whole bag out to store for next time.] Alternatively, you can set a perforated pie pan into the crust.
You may want to moisture-proof your crust when blink baking by removing the crust from the oven when it has about 5 minutes left to bake and applying your egg wash with a pastry brush on the bottom of the crust and about an inch up the sides. Then resume baking the crust for the remaining 5 minutes.
To keep its shape, use pie weights and bake it hot and fast.
