Step 6Cut and Groove the Bottom Board
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Next stand the two sheets of plastic up with the two side boards in place. Measure the distance between the two side pieces. This is the length of the bottom board. Cutting and grooving the side boards first enables the builder to measure the actual length instead of trying to account for the depth of the grooves in the side boards. After cutting the bottom board, put in the two parallel grooves as with the other two boards.
The three pieces (bottom and sides) should be able to fit together around the plastic holding the plastic pieces apart and upright.