What is the purpose of L-Bracket or L-Plate with Arca-Swiss style

Why you might need an L-Bracket / L-Plate

Not many think much about mounting plates.  We all know that camera mounted plate with tripod head or ball head with Quick Release is the fastest way to attaching and removing camera from such a contraption.  Typically such Quick Release plates are only attached to the bottom of the camera as that is the only place where mounting thread is available.  But what if you had to quickly change from Horizontal (landscape) to vertical (portrait) orientation.  That could be really problematic depending on what subject you're shooting.

Usually that would involve:
-Rotating the ball head to the side adjusting where the camera is pointing, reframing and refocusing on the subject as the framing has shifted (to the side and lowered)
-The Camera would be hanging off to the side away from the center of gravity over center of tripod. 

With an L-bracket/ L-plate that process is easier.  Because L-plate offers two mounting surfaces one in horizontal and one in vertical plane it can be attached via either one to your ball head, usually via Arca-Swiss style system.  One would simply need to detach the camera from Landscape orientation and attach is back into Portrait orientation without ever changing where the ball head is pointing to. This way L-bracket offers a very efficient way of photographing subjects in portrait and landscape orientation.  It's an essential piece of gear especially when working with micro (macro), wide-angle and tilt-shift lenses.

A well designed bracket offers these features, or can be equipped with:
-Anti Rotation System
-Strap loop(s)
-Cable Management / anti cable snag
-Safety Stops
-Access to cable ports
-Sliding out for cables
-No tools to slide out, or allen pockets (Slot for Allen Key) to keep it handy