When you're replacing an outer or middle chainring, the threaded inserts will sometimes bind on the chainring bolts and turn as you tighten the bolts, leaving the chainring(s) insecure. Single chainring setups seem particularly prone.
Inserts with Allen heads can be held ﬁrm against the torque of tightening bolts, while those with the traditional indentations on opposite sides will have you reaching for a (limited purchase, slip prone) ﬂat-bladed screwdriver. This Cyclo tool is the answer.
The central pin locates the tool and its two pegs engage the indentations. While it didn’t sit completely ﬂush on our test bikes’ chainsets, it nevertheless worked well.