Remove the webbing you plan to replace. Remove the screws or webbing clips that are holding the nylon strapping in place. Unscrew the screws with a screwdriver or use the screwdriver to pry loose the clips. Unroll the strap from around one end of the frame. Untangle it from the weaving and unroll it from the opposite end of the frame.
Measure along the chair with a string or tape measure to determine the length you need for the replacement strap. Add 2 inches on either end.
Cut a replacement strap to the correct length.
Attach one end of the strap to the aluminum frame. If the webbing attaches to the frame with a screw, fold the end of the nylon strap into a point and push the screw through the tip. For clips, push the clip 1 1/2 inches from the end through the nylon, then fold the end of the strap width-wise until you reach the point of the clip. Attach the screw or clip to the chair.
Pull the nylon strap around the outside of the chair frame. Weave it across the vertical straps to the other side of the frame.
Repeat Step 5 on the other side of the frame, pulling the webbing taut.
Repeat the whole process until all the straps are replaced.