Interlock Roofing Ltd. has created a unique slate-styled product that has the look of traditional slate roofing. The most distinctive feature of the Interlock slate is its internlocking design. Each slate has an interlocking edge on all four sides, as well as being nailed to the roof deck surface. With Interlock Slate, you will Never re-roof again. The Interlock Roofing System Comes complete with a 50 Year transferable Non-Prorated Lifetime Limited Warranty.