So, as you may have noticed in the series, blocks can be easily broken without the proper tool. Namely, when Runt crits the zombie dummy.
So heres my question on how the mechanics work:
A structures has 'durability'. Hitting this structure with a weapon (not tool, weapon) will decrease its durability. Unlike mining, block durability does not reset (if it does, the reset margin seems to be much longer) or recharge (if it does, the recharge rate and/or starting margin seem to be slower/longer respectively).
Some structures can be broken by crits, or their durability only decreases when you crit them.
There were also some other explanations but i forgot em :D