Older boats generally had glass windows held in by a rubber seal that was forced tightly into the gap between glass and hull. This gasket was then locked in place with a hard plastic insert, and these were extremely hard to install. They also required a rounded window shape without any sharp corners and required the cabin wall to be thin, as is the case with fibreglass or aluminium sheet. This method did not allow for the window to open, but on the positive side they were cheap.
If the design called for a window with corners, then a frame was required to hold the window in place. These were generally made of aluminium or wood. Adding that frame meant that an opening window could be engineered, either by sliding the pane of glass along a channel or by adding
