I can't find my picture but on the ends of my jointer, I bolted on a block which meant drilling a couple of holes in the ends of the jointer tables, GASP!!. The extension tables just attach by dropping over the block and a couple screws through the frame of the extension table into the blocks. This won't work on older jointers where the fence is attached on the infeed end of the table. You would have to use some metal side straps in that case or a solid stand like Woodenthings showed. The extension tables have to be flat, straight and slick. You can see I have a leg height adjustment in one of the pics. If I change the height of the tables or move the jointer to an uneven floor area, I can adjust the extensions so they are perfectly in line with their corresponding tables. Being perfectly in line with the jointer tables is important or they won't work. I use a long straight edge to confirm alignment. The extensions can be made in any size you want and easily removed if they are in the way. I have more than one set and have one for the outfeed table that aligns with the rabbet ledge, not shown.
The flush cutting router plate has to be held flat to the jointed area of the board, so it doesn't tip. This jig can be used in many applications where you need to bring something flush with an adjoining piece. Even when I had a 16" jointer, there were always boards I needed to flatten that were wider than the jointer. When you flatten a board before planing, the entire surface doesn't need to be completely surfaced. You can see a rough spot to the right in a picture but it's small and in the center and would have no effect when running through the planer. It will be taken care of when I flip the board and plane that face. Handling 2"x10"x12' pieces of hard maple on a 6" jointer would be very difficult but the extension tables and the router jig make it simple and easy.