I have a Pressman C with the rangefinder, but the rangefinder arm doesn't "attach" at the bottom at all. It has a semi-circle on the lowest part of the arm that rests behind and rides a metal extension on left of the front standard base. Sometimes it can get off the track when it's spring makes it stay forward, next to the standard instead of behind it. All you have to do to get it back in place is to extend the standard out and the arm will remain behind, having reached the end of it's travel. I'll try and post a picture (worth a thousand words) later this morning.