kick at an open door

bang down the door

To present oneself as a strong candidate for a role or achievement, explicitly or implicitly.

close the stable door after the horse has bolted

To attempt to prevent a problem that has already occurred; to design and implement a preventive mechanism that is too late (after the first failure instead of before).

darken a church door

To go to church to attend a service.

darken someone's door

To arrive at someone's residence or location, especially as an unexpected visitor.

don't let the door hit you on the way out

Used as a command to leave in haste, or to indicate that one is glad, or at least unmoved, to see the addressed person leaving.

get a kick out of

To be delighted by; to be amused by.

get one's foot in the door

To initiate contact or a relationship; to gain access, especially to an entry-level job.

get the door

To open a door to help another person to pass through.