I'd guess that it'd work by "attacking" the [STANCE] body parts of creatures standing up and moving too rapidly or failing to spot them with observation skill check. If you just toss them across a narrow passageway as you flee a room, the enemy, if they noticed (you could drop a shower of coin and caltrops such that it appears more that you dropped what you were playing with as you fled than left a trap for them), must stop and either brush them aside or step over them gently/jump the tile. They of course couldn't be a guaranteed "step through this tile too fast and suck it" trap, but even a 35% chance (or more depending on how many you dropped in one tile) would hinder enemy movement and could give you just enough time to GTFO. This would mean that at least SOME types of items lying on the ground would need to be hazardous to walk over. But then again it makes sense that one could not sprint across a field of rusty metal bits, rock debris, or heaps of sticks without risk of tripping or twisting an ankle.
You ever stepped on "
goat heads?" Motherfuckers hurt for minutes, even if they're 1/4 inch long at most, and you NEVER avoid them if you're walking around barefoot out here in the desert. Hell, I can't even walk across my backyard to the driveway without boots. And the poor dog... Unlike the cats and the poodle he's too fucking stupid to dig them out on his own and I always have to pry them out of his feet when he hobbles over to me with a sad-ass look on his face.
You could also use caltrops as pre-set traps, by dropping them in an area you intend to kite enemies back through, but leaving yourself a route that doesn't cause enemies to go all the way around while following you. Then you just lead them through there somehow whilst avoiding them yourself. If there is ever a way to obscure your tracks through high-vegetation/soft-sediment areas to avoid being stalked indefinitely, then you could also conceivably obscure items on the ground, like these caltrops, which could, in terms of actual effect on gameplay, mean the observation skill roll to notice them increases. If adventurers could make use of these and other "quick traps" then strategies for dealing with large bandit groups increase dramatically. Conversely, if bandits can use them in setting up an ambush or in passages into their lair in the dungeons it'd put you at an interesting disadvantage.