Fiberglass mesh is a neatly woven, crisscross pattern of fiberglass thread that is used to create new products such as tape and filters. When it is used as a filter, it is not uncommon for the manufacturer to spray a PVC coating to make it stronger and last longer. The most common place to find fiberglass mesh is in tape products.
Drywall finishers use the mesh frequently. In fact, it is common to replace the paper tape used to float the joint between two pieces of drywall. The mesh that drywall finishers use comes on a roll just like paper drywall tape. The added benefit for the drywall finisher is to roll out the mesh over a great distance before having to apply the first coat of joint compound. Not only does it help them in this manner, but it also causes a stronger bond between the joint compound, the tape and the wall.