Let Carlisle simplify your next Sure-Weld TPO installation with prefabricated Outside Corners. Sure-Weld TPO Outside Corners are pre-molded and are used for flashing outside corners on a variety of details. Installation is fast and easy with no cutting or stretching required. Carlisle’s Sure-Weld TPO Outside Corners are part of the Certified Fabricated Accessory (CFA) program. Certified Fabricated Accessories are the only factory-fabricated TPO accessories that meet the stringent quality tolerances required to be included in a Carlisle warranted roofing system.