a few days ago i found a pretty cool thing to do w/ a old peanut butter jar, make a rocket engine. All that you need to do is cut a hole in the lid that is about 1/2" smaller then the OD of the lid then take a piece of sheet metal (the thinner the easier it is to light), that is cut to be the size of the OD of the threads on the jar then u drill a small whole in the center of the sheet metal, and put the sheet metel disc on the inside of the lid, then screw the lid onto the peanut butter jar so the sheet metal is clamped between the lid and the jar. fill the jar w/ propane, and light it through the hole. make sure the rocket is either clamped down or in a safe place because they have enough thrust to get airborn. Be safe, im not responsible for n e injurys or fatalitys or fires etc. associated w/ this