Replacing the electrical mast flashing where a one-piece boot cannot go over the wires. There are split boots available but they take longer to install, cost more and are vulnerable to failure from snow, sticks, sway and critters. A Garrdal 2 piece flashing 8 nail installation takes under a minute. Repairing a bad flashing only takes a couple minutes and the old flashing doesn't need removed, Garrdal can enclose it. See the template on the installation page.
Rapidly increasing conversions to or new installations of mid and high efficiency furnaces are another example of where a one piece boot can't be pushed over a pipe. Non-condensing units are typically vented through the roof and have a "hood" on the concentric pipe, condensing units need to drain out the wall. Going around the pipe with a Garrdal 2 piece flashing costs less and saves time. Once again, if the existing gasket needs repaired, it can be done in just a couple of minutes without removing the old boot or having to match shingles.
Garrdal is an American made 2 piece flashing that is designed to go around roof top obstacles such as wire masts, high efficiency HVAC stacks or other circular penetrations up to 5 3/8 inches. A split boot alternative that has a single piece appearance. UV resistant with tear away ribs allowing the flashing to adjust from a 1 1/2 inch diameter to 5 3/8.