Just as the Mast Partner holds the mast up and down, the Mast Step is the socket into which the mast fits. Again, this has to be a sturdy construct to withstand the forces exerted by the mast. My mast step is a box made of 2x4s fitted to the bottom of the hull, screwed together and glued into place. The hole in the middle is a 3.5 inch square which will hold the base of the mast. I will use a 12 foot Lodgepole Pine for my mast, cheap, light and easy to obtain in Central Oregon. They work well, too. It is what I use on my Puddle Duck Racer.