Cheap ways to create a working door?

Anyone? I don’t want it to be player-activated if possible. I want it’s release to be on a specific timer.

And the door will be opening and not closing.

This is WILL NOT be in Invasion either.

Spawn a man cannon or grav lift to displace a crate?

Spawn a crate an inch off the ground at a certain time, thus causing it to be displaced and to vanish a specific time after the time it was last disturbed?

You could always do the mine explosion trick, set it up so the mine is fixed, then have a crate behind a grave lift then when the mine explodes the crate will push through and open.

Heres a diagram {} = Crate | = Mine < = gravlift.

| {} < will go to this once the mine is destroyed {}__<