Stuck in the Truck
In our backyard sits this old red truck which is off-limits to children because the door handles don't work from the inside. Children who disobey are likely to get stuck in the truck. At first they will not mind this, as it is fun to play with the steering wheel and the knobs and buttons. Of course, after awhile, they will want to get out and cannot. There they will sit until Mom comes and a) catches them red-handed and b) reminds them that their good Papa forbade playing in the truck and c) discusses why they think Papa forbade this ("door no open" the children say) and d) sets the timer where the children can see it as they serve their "naughty chair" time in the truck.
After they were freed we had lunch. Andy said grace and added a line to the usual litany. "Thank you for no more truck."
Oh how I love natural consequences.