Rail system/retractable spice rack

*small bugfix, on the bottom board the mounting brackets where off center*

First of all, special thanks to Ken9226 for his upload of the spice holders:
www.thingiverse.com/thing:2763553

This is my second contribution, currently learning FreeCAD.
I wanted to make a retractable spice rack to save some space in my kitchen. Then I realized that the rail system can be used for a whole range of things.

In my setup I will have 2 double racks and a single rack, the double and single bottom board are included. The standing board is to big for my printer so I didn't bother designing it with holes and stuff. I will use an 8mm wooden board, cut to size.
The linear movement is 290mm (11.5")with an inner wheel spacing of 50mm(1.97") (standard upper cupboard in europe is 300mm (11.8")) The built-in length is 220mm(8.7").

the shafts for the inner wheels are M4 threaded rods (1/16"), mounted in the bottom board, then placed the spacers and then the ends are placed inside of the inner whe