Screw a 40-inch two-by-four to a sheet of plywood to form the floor, and cut arches from two additional sheets of plywood to form the ends of the fishing shelter. Cut a doorway into one of the arches, attach the arches to the floor with hinges, and attach a 7-foot long two-by-two to the top of the arches using brackets. Cut a hole large enough for fishing in the floor, and staple canvas over the shelter.
To make the ends of the shelter, measure 20 inches below the center mark, tap a nail into the plywood to mark the spot, remove the nail, and cut an arch that apexes at the hole left by the nail on each sheet of plywood. Attach the arches to the floor using three hinges on each side, with one hinge on each side attached to the top of the two-by-four previously installed on the floor of the shelter.
Cut a hole that is 2 feet wide and 4 feet tall for the door, and attach the door with hinges. Add a door handle, and cut portholes in each end of the shelter. Staple a tarp or canvas onto the frame. To fold the shelter, remove the center beam and fold the arches inward.