Step 1: Get Items

You will need two 4X4'S a rod(for your arm) then your Catapult arm and a Piece of plywood and one eye hook and a 11 1/2 inch bungy cord

Step 2: Cut Everything

Your catpoult arm should be 17 INCHES your peice of plywood should be 3FT long and 20 inches wide your arms that hold your arm should be 18 inches tall (those are 4X4's) then your legs (also 4X4's) 2FT tall and you need four of them

Step 3: Now Assembling

Take your legs and put them on all four corners rite at the edge under then put your arms that hold the catapoult arm 2 1/2 inches in from the sides then get a three centimeter wide dye rod then drill one hole in each arm 1 1/2 inch down from the top of your 4X4 and drill them down to your plywood and then put your 7 inch arm in the middle of the dye rod then put a eye hook in the plywod then put a 11 1/2 in bungy cord on that and drill a hole in your throw arm to put your bungy cord too and then you put your cup on the end of your throwing arm to put whatever you throw in it (in mine i use golf balls)