Wood is very strong, even when sawn into 3/16">4mm<sheets. When you lift a sheet of wood like that off the log it flops and bends and if you exert force on it a certain way it can be split very easily... By using the box joint to literally wrap a sheet into a box, the floppy sheet becomes rigid. A heavy walnut base weights it and holds the bottom square, a small frame set an inch into the top end squares and stiffens that, two lift out top panels were provided, one with a 1'1/2" round hole and the other with a 2.1/2" round hole that sit on the top inner frame, a block of foam is set in the bottom to hold dry stems firm. When it is all tight fitting and well glued it becomes and amazingly light and rigid structure. This is made of northern red oak, is 14" tall and about 5.1/2" square, and finished with four coats of Polycrylic, a clear flexible interior finish. In this case the fingers are left long for a 'log cabin' effect, two others were made with flush corners.