Cast iron benches often have ornate 19th century designs, such as the ones on the Thames Embankment next to the Houses of Parliament. The wood pieces on cast iron benches are usually hardwood; narrow slats of hard-wearing timber that do not warp or rot as quickly as softwood. However, even hardwood needs replacing after many years of use, especially if it has been subjected to the British weather.
Slacken the nuts on the two bolts holding one of the slats in place, at both ends of the bench with a spanner. Remove the nuts, bolts and slat. Measure the length, width and depth of the slat so you know what dimensions the new slats need to be. Count the slats so you know how many new ones you need.
Measure the distance from the end of one of the slat housings to the centre of the bolt hole. This tells you the distance you need to measure from the ends of the new slats to mark the points for drilling the new holes. Measure the diameter of a bolt hole. This tells you the size of drill bit you need to use.
Mark the drilling points on the new slats and drill the holes. Sit a new slat where the old slat used to be and align its holes with the holes in the two slat housings. Slip bolts through the holes, finger tighten the nuts, then tighten them further with the spanner.
Proceed in like manner, removing an old slat and fitting a new one until all the slats have been replaced.