nonamethanks said:
Crossbow bolts are noticeably shorter than arrows, they're more akin to darts. post #1638013 is an example that is clearly visually distinct from your average arrow. Sometimes they even lack feathers: post #5882556.
Even if they're normally shorter, that isn't the case of what is being tagged a crossbow bolt: post #7490850, post #3207926, post #6313151. For these images it's effectively arrow + crossbow = crossbow bolt when there is visually no difference between what is shown and an arrow. The same with dart depictions, post #3564033.
Lacking feathers isn't unique to crossbow bolts though. For examples we do have posts for things like toy arrows, post #4466710, and energy arrows, post #7616240. Neither of which necessarily need feathers. In real life too though there are arrows that do not have fletching. Traditional Japanese archery for example uses arrows without fletching for practicing archery form. The archer for that kind of practice releases the arrow at a point blank target, this allows one to evaluate how the arrow is leaving the bow so the archer can correct themselves.