The A-frame, or gallows frame, functioned to support the walking beam, linking the engine to the paddle shaft. It also incorporated the crank frame to support the paddle shaft. On the Maple Leaf the massive structure was constructed of large wooden timbers held together with a complex system of iron tie rods. It was removed by Roderick Ross in 1883.
Many twisted and/or broken tie rods lie between the paddle shaft and the front of the boiler to mark the A-frame's position (85 to 102 feet on the baseline). One timber forming the forward starboard leg is located in front of the boiler and measures 16 by 12 inches. It slopes down toward the bow and appears cut off flat, near the river bottom.
Two timbers mark the crank frame at 114.8 feet on the baseline, just behind the boilers. They measure 9 by 14 inches and are spaced 6.7 feet apart. The timbers slope down toward the stern and the tops are sawn or broken off flat just below the river bottom mud line. These are shown in Figure 6 as the A-frame timbers aft of the boiler.