Definitions for "Base leg"
The part of the landing pattern that's at 90 degrees to the final approach.
A flight path at right angles to the landing runway. The base leg normally extends from the downwind leg to the intersection of the extended runway centerline.
A flight path at right angles to the landing runway off its approach end that extends from the downwind leg to the intersection of the extended runway centerline.
Keywords:  rafter, horizontal, length, run
Horizontal run length of a rafter.