We have two 30-year-old poolside chairs. They might be 40 years old. They are excellent metal chairs with adjustable backs. The problem was that the plastic sliders on the bottom of the legs had long ago disintegrated, leaving nothing but bare metal. So, when my wife or kids dragged the chairs across the concrete, the legs would make a brain-curdling screeching sound. I had been thinking about making wooden plugs to stick into the hollow legs like corks, but then I realized I could easily make custom sliders with my 3D printer.