There are many occasions when you need to replace, or otherwise use Plexiglass, Perspex or other types of acrylic materials. One instance that spring to mind is when making replacement ports, hatches or other parts. This video shows the method that I use to polish the edges, which works extremely well. One thing that is not mentioned in the video, however, is that polishing the edges greatly reduces the chances of the acrylic crazing in the future, a common problem on boat windows. Most crazing starts from the edges, polishing seems to make this far less of an issue down the road.