This is Karl's design for the Boeing 737 'J' Rails. Each side consists of four rolling truck assemblies supported by cheap roller stake bearings. The lower truck assemblies stop the seat from lifting away or becoming detached. There are two guiding bearings that sit in the rail to guide the trucks.
The original prototypes were created using only PLA at 25% infill and Karl found these more than suitable to support most peoples weight.
This design provides a very smooth operation, ease of access to the cockpit and a very cheap alternative to other options.

Karl is busy designing the Ipeco Seats! But a moch full size seat is included in the design for refernce.
If you need the First officer side, flip the design template over.