Measure the width of the existing straps and buy replacement strapping. Cut existing damaged strapping and remove the strap and steel tabs from the chair frame. Set the tabs aside. Discard the damaged straps. Clean the chair with a mild detergent and water.
Measure the distance from one rail to the other, using a cloth measuring tape. Wrap the tape around the chair rails one-and-a-half times, in the same manner as the straps were attached to the frame. Multiply that measurement by .85 and add 1 inch. For example, if your hole-to-hole measurement is 36 inches, multiply that by .85 to get 30.6, then add 1 inch to get a measurement of 31.6.
Cut a strip of vinyl to measurement from Step 2. Drill holes in each end about 1/2 inch from the end and trim the corners diagonally toward the hole.
Soak the strap in hot water for about five minutes. Attach it to one end of the chair by pushing the steel tab through the end of the vinyl and through the hole in the back of the chair. Wrap the strap completely around the frame, covering the tab.
Pull the strap tightly over the chair to the opposite side. Stretch it and wrap it around the frame one-and-a-half times.
Push the steel tab into the hole of the vinyl strap and into the hole in the chair. Slide the loop over the tab and release the strap. The strap will contract as it cools.
Repeat the process for any remaining damaged straps.
Measure the chair mesh by using a cloth measuring tape. Measure from side rail to side rail at the widest part. Find the length by following the curve of the chair with the measuring tape.
Cut the old sling down the center with a utility knife. Remove the end caps off each side rail and slide the halves of the sling out from the tracks on each side.
Loosen the bolts that attach the rails to the frame and pop out the spreader bar---the thin bar that runs across the back of the chair from side to side.
Remove one rail entirely. Holding the replacement sling with its hem side toward the back of the chair, slide the nylon rod onto the track of the rail that is still attached to the frame.
Slide the detached rail over the rod on the opposite side and bolt the rail back onto the frame. Tighten the bolts on both rails to make the sling taut.
Reinsert the spreader bar by spreading the rails apart and bending the bar to pop it back into place. If necessary, tap it with a rubber mallet to restore its shape.
Trim the rods with a wire cutter, then push the end caps back on the rails.