The baseplate allows pedals being mounted on the Sim-Lab seat slider, which makes it easy to quickly adjust the position of the pedals relative to the seat.
Sim-Lab pedal slider baseplate | G-Performance
Sun Dolphin Slider Pedal Boat with Canopy, Ocean, 72142 at Tractor Supply Co.
That Pedal Show Special – Slide Guitar With Ariel Posen - YouTube
Steve Fishell explains how pedal steel guitar works - YouTube