I agree, they are not used much but when they are, nothing else will do. I used one once to remove a lock cylinder nut on the underside of a an old Ford trunklid. the access hole was not big enough to get a regular wrench in and then turn it; besides the nut was offset from the access hole. I have the regular and metric crowfoots, as well as the regular and metric crowfoot flare nut types. All crowfoots are not made equal. Try to get the ones which have the square drive hole in two places, both in the plane of the wrench and the usual one perpendicular to the plane of the wrench. This way you can use crowfeet as regular wrenches too in case you are missing some sizes or need a second backup wrench. I tried to use the side hole once to put a flex bar on it to use as a fan clutch wrench, but the whole lashup was a bit too thick.