I am building a butterfly extension table. The 2 pieces of the tabletop that will extend and retract are 36" w and 33" long. They will be connected to a rack and pinion wooden assembly so if either end is pulled out, the other end will extend equally at the same time. Hidden within the now emerging gap will be a hinged butterfly extension assembly 24" long, with 2 pieces hinged that rotate up and open like a butterfly's wings. That will flatten onto the side rails and the two end pieces will then be pushed back to engage the butterfly extension. Underneath the table will be lock assemblies that once engaged will prevent the 3-piece tabletop from moving. Here's an article about a similar table but without the rack & pinion that synchronizes the extension and retraction. https://www.finewoodworking.com/proj...xpansion-table