No answer? Kay.
Got a artifact toy hammer. 6000 dwarfbucks.
Some toy!
Also:
2 questions: can a door stave off invaders? And I'm seeing 3 insect hives, 2 bee hives and a ant hive flashing on screen. What does that mean?
A locked stone door will indeed fend off some invaders if it is locked before they arrive, however, some invaders are building destroyers and will just smash your doors down.
Don't use locked doors. Trolls make nasty party guests.
Instead, use a raised drawbridge* or floor hatch** oriented so the enemy comes from below at the top of a stairwell.
*You can build a drawbridge by going to (b-->g) and then using (k u h n) to size it and (a x d w) to control what side it raises on.
**Make a stone floor hatch at a mason's workshop and then place it with (b->H)(this is case sensitive).
The flashing insect hives are not really important - I'm not sure why they're flashing, but you can catch the bees and put them in hive boxes for honey if you have a beekeeper.