Place a 3-way corner connector on both ends of two 40-inch pipes, with the pipes inserted in the left hole. Place a 3-way corner connector on both ends of two more 40-inch pipes, this time with the pipes being inserted in the right side holes.
Place a 12-inch pipe in the center piece of the connectors on two pipes. Join the remaining two 40-inch pipes to these pipes so that you have two 40-inch by 12-inch rectangles.
Insert a 38-inch pipe into the remaining connector hole on each piece.
Place a T connector on each end of two 12-inch pipes, using the center holes.
Connect the 38-inch pipes together using the 12-inch pipes and T connectors. At this point, you should have a 12-inch tall rectangular frame measuring 40 inches wide and 76 inches long.
Attach a snap on connector to both ends of each of the remaining 40-inch pipes.
Snap these pipes into the top portion of the frame, spacing them about a foot apart, to support the mattress.