WW: Colloportus

You touch a closed door, window, gate, chest, or other entryway, and it becomes locked for the duration. You and the creatures you designate when you cast this spell can open the object normally. You can also set a password that, when spoken within 5 feet of the object, suppresses this spell for 1 minute.

While affected by this spell, the object is impossible to open by normal means unless a spell like "Alohomora" is cast.

When cast at higher levels it is harder to unlock by spells.