Bottom shower flap pivot door

You should be able to use a #6 X 3/8" pan head stainless steel screw. You can get them at any local hardware store. The drill bit should be 7/64" for drilling holes. The drip rail is installed on the bottom inside door facing the shower side. You may need to cut the drip rail to size and install it where the old rail was. If you need to drill new holes, it's preferable to drill into the drip rail and re-use the holes in the door. It can be risky drilling into the door itself, since there is a risk of hitting the glass. Glass is usually 1/2" in the frame.