“I’m going to change door locks and add more doors to be locked inside the building, to make sure nobody travels to far unsupervised. Locks will be added to cupboards. Everything will have to have a place, neatly locked away.”
There is an item called a “police bar.” One end jams under your door knob and the other end is stuck into a recess in the floor or maybe just a block of wood nailed to the floor.
Below you will find a link to an example.