He will tie the knobs to the corners and twist them/tie a few together.

He will first try to use it to hook on the trap door if there is a latch or anything.

If it's sealed or if the brainwashing will prevent him, he will turn his focus to where the Sinners are. When the elevator opens, he will throw the end with the weights on it to a close cell. Would he be able to fight brainwashing if he stays on the elevator?
Could a sinner place their tablet in the end of the sheet they can reach and would he be able to take it with him to another floor?