The Interlock Group. Interlock®, Interlock Lifetime Roofing Systems®, Alunar® are registered trademarks of I.E.L. Manufacturing Ltd. and are used under license. Cannot be combined with any other promotional offers or discounts. Offer valid for this promotion only. Discount cannot be applied to previous purchases. Price discounts depend on size and location of your home. Minimum 12 Sq. purchase required for discount offered. Must purchase an Interlock Lifetime Roofing System to qualify. Available only at time of purchase. Offer not valid if contract cancels. Offer does not apply to contract amendments. Offer expires October 31, 2024.