These are two components to let you use MISUMI Part No.HFS5-2080-1500 t-slot. Unlike the factory option (which costs more than $250 without brackets), the entire table can be built for around $100 with shipping. I used 3 lengths of the referenced part number, for a total of 5 pieces 27" long, and an extra left over. The small pieces are for holding the lengths together side-by-side. I used 16 total, 4 per joint. The other piece is to hold the table to the side rails. I have elected to use 5 connectors on each end. For printing, I used PLA, .3 mm layer, 60% infill. These seem to be plenty strong for the application. Attachment is with #10 sheet metal screws.