Farpoint's mounting rings allow the piggy-back mounting of small telescopes onto "D" sized dovetail bar equipped telescopes.  The rings are mounted on quick release adapters that allow you to mount them in seconds.  Once the rings are mounted on your larger telescope's dovetail bar, the three white delrin tipped support screws in each ring hold your smaller scope in place.  The support screws are adjustable in order to align the piggy-back telescope to the main telescope's optical axis.  Ring kits are sold in pairs and allow the mounting of telescope tube that are 20mm smaller than the ring size.