"Extra" Boulders in Traps
 

Even after all this time, I'm still not sure how "extra" boulders in traps work, that is: what makes them trigger?

By "extra" I mean the boulders that you can load in a trap in addition to its normal load.

(This is about Sangband.)

I presume we're talking about Sangband. My understanding (from play, not from source-diving) is that a boulder is dropped in addition to the trap's main load going off. That means that one-shot traps can continue to function with boulders after their main payload disappears, and repeating traps (e.g. melee weapons) can add boulder damage as well.

Could be wrong though - it's a while since I tried to add boulders to other trap loads.

Hmm, when I played a burglar I never tried putting boulders in as well as other things; I assumed you could put either 1 weapon/device etc OR any number of boulders, and once I found out it wouldn't drop all the boulders at once, I stopped using them because they were so heavy.