The Arca-Swiss L-Bracket is a universal L-shaped bracket that allows you to mount a DSLR or medium-format camera to a head in portrait orientation. One segment of the bracket features a 1/4"-20 screw to which to mount your camera, and both this part and the segment perpendicular feature an Arca-Swiss plate at bottom for mounting to a head.
The two Arca-Swiss plates are adjustable, as they slide on rails and lock in position via a lever. This allows you to execute nodal point adjustment if you're creating rotational panoramas that involve stitching. In moments, the plate and the attached camera can slide completely off the rails for a quick change to handheld operation.
The Arca-Swiss plates perfectly fit Arca-Swiss Quickset Classic quick-release systems, and they also fit most other Arca-Swiss-style clamps. The L-Bracket also features a 3/8"-16 thread.