how do you open a closed door?

[dan83m]

i have a crowbar but there aren't any option like lockpick or pry the door using a crowbar... how do you do it?

[Pandorea]

You "attack" the door with crowbar. Not technically "opening"..but.. it is what it is for now.

[geras]

You break the door down with any weapon (not sure if guns work) or kill zombies inside given building for a chance of a key spawning in their inventory. If there are no zombies in given building you can lure zombies from outside into the building and kill them then.

[non_curo]

Axe is the best weapon to break doors, 7 or 8 kicks are good enough. Sledgehammer is the ultimate option.
You can also dismantle wooden doors with a hammer and a saw, and metal ones with a propane torch and welding mask. Just right click on it and choose this option : you open the door and gain xp in the process.