Attacks of Opportunities allow a single melee attack. This includes:
It does not include:
1. Determine weight in lbs of object
a. Determine volume
b. Multiple volume with density
c. Voila! There’s the weight!
d. Example for one of the stone doors to the Inner Sanctum in the Temple of Urgathoa (using the metric system, b/c - hey – that’s what 95% of the world uses):
Volume of door: 200cmx150cmx4cm = 120,000ccm
Density of stone (average between sandstone and granite) = 2.8g/ccm
Weight of one door: 120,000ccm x 2.8g/ccm = 336,000g = 336kg = 741 lbs
2. Look up the corresponding average weight for creatures ( space, reach, and threatened area)
For the above example, 741 lbs equals a Large Creature
3. Look up how much damage an object of that size category makes (environmental)
For the above example, a Large Object does 4d6 damage if it falls from at least 30ft and is made of a dense, heavy material such as stone.
If it falls from less than 30ft, the damage is half, if it falls from more than 150ft the damage is twice as much.
For less dense material the damage is lower. If you want to crazy on this step, this table is your best friend: https://www.engineeringtoolbox.com/density-materials-d_1652.html
Note that it lists the density of apple seeds!
4. Attacks are resolved as follows:
a. Ranged touch attack (<30ft +2, >150ft -2)
b. Target gets Reflex save for ½ damage (<30ft -2, >150ft +2)
c. Roll damage