>>38663
It's a fairly niche functionality on nekochen and easychan that allows you to just paste a tok id or link and hit attach instead of downloading it yourself and then posting it, not worth to add to endchan in general imho. You can go to easychan if you want to see how it works.

There is also the possibility of seeing all the previous times a file has been posted with a different file name, that one is more interesting.