Use high-quality wood to replace a broken patio swing seat. Cedar is ideal, since it is resistant to moisture and insects. Obtain planks measuring 8 by 2 inches.
Cut the planks using the same length as the previous seats to make sure they fit the chains. To obtain a smooth finish, sand the seats with fine-grained sandpaper. Using the old seats as a guide, make four mounting holes for each seat. Allow the finish to dry before fixing the new seats. Once the finish is dry, attach the new seats to the suspension, making certain they are level and secure.
To maintain the safety of the swing set, replace the chain brackets. Note the correct sizes of the bolts and nuts to attach the swing seats to the chain brackets. Bore holes in the edges of the seat, and fix the chain brackets with the bolts. Next, decide the length of the swing set from the crossbar to the appropriate base height of the seats off the ground. Purchase 3/4-inch Dacron and polyester blend rope. Separate each rope length in half. Make 3/4-inch holes in the planks, and hang the ropes over the swing set crossbar. Make sure the ends are even. On both sides, make a single loose knot on the rope, and pull it up to the crossbar. Make a double knot in the ropes, and insert the ends through the drilled holes. Finally, secure the knots using a propane torch.