Applications Tubular Trundle Arms are for mounting the Top Spring unit. They are also an ideal replacement for the old day bed. You can take the daybed spring off and use these Tubular Trundle Arms for better strength and stability or a completely new look. How Sold The Trundle Arms are packed in pairs and include the necessary hardware for attachment. Trundle Arms Fit the Narrow 33" Daybed End The 33" Trundle Arms fit the narrow 33" daybed end and keep the rails at a standard height or about 15 1/4" off the floor.