When installing your shower, it's vital for your tile to be level. That's why you need the reusable Goof Proof StringA-Level Standard Starter Kit. The innovative design attaches to your wall and allows you to stack both large and heavy tiles vertically. Whether your walls are straight or rounded, the StringA-Level will quickly conform to their shape. Special leveling bubbles built into each piece in this starter kit ensure a precise fit for any average-sized shower.