Swing N Slide created the Rapid-Loc system, which was designed specifically for use with 4×4 lumber dimensions. Swing-N-Slide swing sets are made to last. You can be confident that by using larger dimensional lumber in the construction of your swing set your backyard playground will remain more structurally sound in an upright position when assembled according to our detailed illustrated plans. We put kids first! Highest Quality Standards and Swing-N-Slide swing sets are Safe.