One of the solar absorber floats is 4.5 inch wide by 15 inches long. 0.75 inch x 1.125 inch strips are nailed across both ends. This makes the active tar-paper-covered area only 12.75 inches long, but the cross strips are essential. Without them, the absorber plate would sink to the bottom when weighted sufficiently to submerge it. The cross strips are on top and stick out of the water when the absorber plate is about 0.12 inch below the surface. The ballast weights are such that at this depth the weight of the absorber float is equal to the weight of the water displaced. If the float tries to sink deeper, the cross strips displace more water and the increased buoyancy brings the float back to the correct level.