Glass that starts out broken

This tutorial assumes you already know how to create breakable glass, if not then follow that tutorial first.

1. Open one of your maps or make a new one.
2. Make a func_breakable_surf with a frame around it (as if you are making a normal breakable window).
3. Set up an env_explosion in the middle of the window, then change the options of the env_explosions as follows:
   Name: Anything you want as long as you know what it is
   Magnitude: 1
   Then in the flags tab, change the flags as follows: Check No fireball, No smoke, No decal, No sparks, No sound, No fireball smoke, No particles, and No Dlights.
   

   Broken glass that breaks when the map starts
4. Set up a logic_auto near the env_explosion (it doesn't matter where you put it, but I recommend that you put it in a convenient place)
5. Change the entity outputs for the logic_auto as follows (if you aren't sure how to use the input/output system, read this):
   My output named: OnMapSpawn
   Target entities named: env_explosion (the name you typed for that entity)
   Via this output: Explode
   Check the box that says, "Fire once only".
   Then in the flags tab, change the flags as follows: Check "Remove on fire"
6. Test your map! When it loads the env_explosion will break the glass leaving the jagged glass edges on the side of the frame.