Abstract: Multi-joint stands 126, 127 of drill pipe are assembled and disassembled in a drilling rig 15 by use of a powered mousehole 11 concurrently with well drilling operations conducted by use of a drill string top drive system 23. The powered mousehole 11 has an upwardly open bowl 45 in a floor 17 of the drilling rig which can be rotated about a vertical axis 55. A pipe joint 110 held in the bowl, and depending from it, can be screwed, with controlled levels of torque, into connection with a second pipe joint 113 suspended vertically above the first joint 110 by a hoist system 13 which is separate from hoisting equipment 19 carrying the top drive system 23 over a well bore 21. The second pipe joint 113 is held from rotation by a tong assembly 12, but can move axially against a yieldable support 40 into threaded connection with the first joint 110.