I built this flashlight based on a solar garden light for the boost circuitry and LED. The switch is an American light switch. It uses a single AA battery. The battery door is a 2 1/2 inch hinge. The battery spring is loose in the battery compartment, not attached to the hinge. The positive end of the battery is pressed up against a piece of 14 gauge wire that connects to the switch. I started with a block of wood that's 10 3/4 inches x 2 3/4 x 1 1/2. It's heavy and not very bright, but I plan to use it as a night light. In order to replace the battery, you have to first remove the screw, then open the battery door without losing the spring. Then use the screwdriver to push the old battery out from the other end and then push in a new battery, positive end first. Then put the spring back in, close the battery door, and screw it back on. 
