3 Volt red LED and 2 x 1.5 v button cells.
Step 1: Battery Bit
Use a 1 1/2" x 3/4" baton, about 1 foot long.
Push one leg of the LED down the small hole.
Push the batteries into the 1/4 hole, and suspend the other leg over the front of the batteries.
Step 2: Target Disks
Staple a ribbon of cut up soda can, to the back of the disk.
Attach the disk to the front of the batteries.
Step 3: Armour Plate
It protects them against damage for a while.