Connect the four joints of the individual bars to assemble the stretcher frame. Tap the corners of the frame together with a hammer. Use the staple gun to secure the frame at the corners. If braces are necessary to support the center of the frame, attach them in the appropriate slots on each side. Secure the braces if necessary with screws and screwdriver.
Lay the canvas face down on a clean table. Use scissors to cut the canvas, allowing for 2 to 4 inches of overlap all the way around the frame.
Place the frame on top of the canvas. Center it on the canvas.
Fold the canvas over one side of the stretcher frame. Staple the canvas to the frame, using the staple gun.
Turn the frame around. Pull the canvas over the opposite side of the frame. Hold the canvas tight and staple it to the frame
Turn the frame to one of the uncovered sides. Pull the canvas up and staple it to the frame.
Rotate the frame to the remaining uncovered side. Pull the canvas as tight as possible over the frame and staple it to the frame.
Work around the frame, pulling the canvas tighter on all sides. Staple the canvas along the length of the frame on all four sides so that it is tight.
Pull the canvas at the corners tight. Fold the canvas flat onto the frame. Staple it down, using the staple gun.