Vinh NguyenDIY Rails - Do-It-Yourself Rails; contact surfaces for pistols kits typically, which can be made at home on a CNC mill or a lathe.
Upside Down - Asking for a pistol frame printed "upside-down" means to have its magwell pointing away from the print bed.
Right-Side Up - Asking for a pistol frame to be printed "standing" means to have its magwell pointed down towards the print bed.