If you need to make a custom window or door sill pan, or flash any pipe, wire, or deck Ledger there is not a better product than Elastoform. This is one of my favorite product finds of the past few years. I found this in Carlisle's catalog when I was working on details for a house WRB using CCW 705 Peel & Stick. The video shows me using it on a porch install, and the photos in the slideshow are from my Perfect Wall house I recently completed. (See these posts here to learn more about the Perfect Wall project.) Carlisle makes this product for EPDM roofs and it's originally intended for pipe penetrations and roof flashing purposes.
It has some similarities to DuPont's Flexwrap that I've used for years to make window sill pans. However, it's much thicker (it's a 90 mil thick product) and it feels "bullet proof." I love how it retains its shape when you flex it into a corner. I first used it on my Perfect Wall house for window sill pans but quickly realized its use for flashing: awning bracket, deck brackets, pipes, etc.
Elastoform is a premium priced product as you'll find this running about $3 to $4 per LF. It's also not generally stocked so you'll need to special order it ahead of time. Some products are worth the premium price and I think Elastoform is one of those when you consider the cost of a callback or worse, the cost of defending a construction defect lawsuit
Risinger Homes is a builder and remodeling contractor based in Austin, Texas. Specializing in architect-designed homes and fine craftsmanship, Matt relies on an in-house carpentry staff and the latest building-science research to build dramatically more efficient, healthy and durable homes.