More than open and close
A door says a lot about a scene. A creaking wooden door suggests an old house; a pneumatic hiss, a spaceship; a car door, a street. Door effects are some of the most-used foley sounds, and free libraries hold many variants: knocks, handle turns, locks and keys, slams, creaks, sliding and revolving doors.
Matching the space
Doors carry the sound of the room they are in, so pick a recording whose space fits your scene, or a dry one you can place with your own reverb. Separate the parts of a door sound, handle, swing and latch, and you can retime them to match a picture exactly.
Producers also sample doors for percussion: a slam makes a convincing kick or snare layer, and creaks become eerie drones when stretched. Every card shows whether the recording is cleared for that.