The expansion washers are used to allow movement between multiple layers or various wood products such as countertops and tables.   These washers are an economical replacement for the steel washers often sold for this purpose.   To properly use these washers a slot needs to made for the washer to sit in and a slot for the screw shank to slide.   The screws used should have a flat shoulder to contact the washer and only tighten slightly to allow movement with temperature and humidity changes. We designed these washers in-house to be an economical yet durable alternative to steel expansion washers. We have been using them for years ourselves without a problem and now invite you to try them for yourself.