Lay out the 6-ft. sides so that they taper slightly toward the top. Then lay out your 3/4-in. dowel rungs 12-1/2-in. apart, with the first one 15 in. from the top and the last one 18-1/2-in. from the bottom. Measure and mark the placement and lengths of each rung. Use a power saw or handsaw to cut the rungs to 14 in., 15-1/2 in., 16-3/4 in. and 18-1/4 in. Sand the ends of all dowels.