While Glass is mainly scenic, in maps such as rooftops, where it functions as temporary platforms. Glass is fragile. If you kick objects onto the glass, it will break. If you kick a player onto the glass, it will also break. Bullets can easily fly through the glass. Grenades however, will need a specific requirement for it to break through the glass successfully. If you just toss a grenade onto the floor, it will roll over the glass. You would need to launch the grenade from a certain height for it to smash through the glass, and continue traveling to whatever fighter you're trying to kill.
As of the new fire update, Molotovs cannot travel through glass. However, if a Molotov is thrown at a glass, the fire will slowly damage the glass, causing it to eventually break.
Reinforced Glass Edit
Reinforced Glass is considerably much harder to break, for isntance, it is much more resilient to bullet and projectile damage (however not resistant to Explosions). The exact amount of bullet resistance is not measured as of yet, but even for most primary weapons it takes around half of a clip of ammunition to fully break just one piece of glass.
The glass has a total of 2 other sprite frames which signify how much damage has been dealt to it.