this is a rubber like gasket.. it is used in commercial glazing mostly or alluminium windows. It will go around corners, they call this face vinyl in the Glazing trade, it usually pushes in between the glass and the frame or between the glass and the bead that clips in to hold that glass in place, there is usually one on the other side which is called back vinyl and that one often fits into the extrusion, you can pick this up at any Commercial Glass shop or for that matter any Glass shop that does any storefront work. It comes in many sizes depending on the thickness of the glass and or the build of the frame. If you have a specific place you want to install this I would go to a glass shop and get a few inches of each size and try to push it in, it should go in with a bit of resistance, soapy water in a spray bottle will help if it gets hard, it can be installed carefully with the end of the handle of a screw driver or rubber side cutter handle but they make a purpose made roller tool that works better if you have a lot of it to do which is not that expensive, can be bought at any Glazing supplier. What are you intending to do with it? a nice laid bead of silicone can sometimes be more effective, Ususally this stuff is used in Glazing systems that have ways to move water out so this product is more like a secondary seal it slows the water from going through the system or tries to stop it from entering, most systems that use this count on another seal and drain holes to stop water from entering building.
