Sounds like Butyl Tape. Excellent stuff. Cheap too. Comes in black & grey. Don't use black you'll get streaks. It is available at many RV stores and a large roll sells for about $7. I was adjusting a dog on a hatch when it broke, and then it started raining...hard. I took a wad of butyl and went outside in the rain and built a dam at the gap between aluminum & glass and it sealed it up completely, in the rain. It will stay pliable for 30 years. You run a piece of the tape on the area to be sealed and tighten the equipment. Then trim off the excess. You can save the excess for things like my leaking hatch. It is NOT for fastening, only for sealing. There needs to be some other mechanical means of fastening the items being sealed. Now if you want the absolute best butyl tape, go here: http://sbo.sailboatowners.com/index.php?option=com_marketplace&page=show_ad&catid=0&adid=2682&Itemid=204 . Worth a look. Mainesail is a research fanatic and has done extensive testing of many brands of butyl and now sells the best version available. I suspect that after amortizing all his research time and expenses, he's loosing money. He has a lot of other interesting info based on testing he's done. A good resource.