Measure the length of the bed frame railings. Determine whether you want to cut them or attach them to the wooden posts as is.
Cut the bed frame railings with a metal cut-off saw to the measurements you choose, if you want to do so. Leave at least 20 inches in length to comfortably fit at least three sets of weights on each shelf of the rack. Confirm that the bed frame railing measurements are all exactly the same. Smooth jagged edges with sandpaper.
Attach the bed frame railings to the two wooden planks. Mark the distance between the bed frame railings on the wooden planks. Use measuring tape to ensure that your measurements are exact. Leave at least 1 foot between each shelf to make room for each set of weights. Use a cobalt drill bit and thick, heavy-duty screws to attach the bed frame to the wood.
Screw one piece of wood into each side of the wooden poles of the dumbbell rack so the rack doesn’t topple over. Keep the pieces of wood flush with the main rack pole.