Over time, dirt, debris, weld flash (tiny pieces of vinyl) and other particles can build up in the window tracks, causing windows to catch or resist sliding. Remove the sash to gain full access to the tracks by sliding it past the anti-lift clip, then pull up and out. Use a soft-bristled brush or vacuum cleaner to remove any dirt or debris. You can also use a damp cloth to wipe the tracks clean. Tougher build up can be cleaned with a combination of soapy water or vinegar cleaning solution.