Mr Maziere showed me a clever trick for holding a door and frame vertical, using V's of battens held together by rubber bands (sections of car tube). The door was closed to keep it square while it was built in. Mr Maziere found himself inside the room after bricking it in, and I could not find the key to open it to release him. The outside door was locked as well and the key could not be found. A way was eventually found to pick the lock.