Abstract: The invention is a method and device for supporting construction materials used to form a masonry arch on a wall. The method for constructing an arch includes extending an elongatable body to a select length and tightening a lock to secure the length of the body. The next step is inserting a first end of a leaf spring into a first slot between a first end strap and a first toggle clamp and then clamping the leaf spring into place with the first toggle clamp. The next step is inserting a second end of the leaf spring into a second opposite slot between a second end strap and a second toggle clamp and then clamping the leaf spring into place with said second toggle clamp. Finally, the arch support device is mounted on a mounting surface near the wall where the arch is to be installed, and the mason places a plurality of masonry objects on the leaf spring to create an arch.