It is a jig for facilitating different woodworks (sanding, planning or cutting etc) on the foldable workbench.
Painted with different colour to be distinguished (flat=yellow, helping=blue).
Painted the flat area (yellow) and the supporting wooden pieces (blue), while the circular holes help better fixation on the foldable workbench, holding the wooden pieces under this surface with clamps, placing in different positions according to the kind of work..
Wooden pieces can be tightened in a fixed distance with a clamp, providing the certain repeating cuttings.
The secondary plate, with a horizontal (over it) and a sliding bar (on the side) [blue] help the circular saw to slide and cut the wood accurately (12cm from the sliding bar).
The weight of the circular saw as the pushing of the plate by hand keeps the wood steady enough to make the cutting accurate and in one movement.
The horizontal sliding bar can host thicker than (~2cm) flat pieces of wood and wider (10-15cm). It is longer than the sliding plate and can ride over the piece wood to be cut and the steady traverse.
Again the weight of the circular saw, as well as the hand pressure is enough for steady position in there, to succeed a fine and safe cutting. For more secure clamps can be used additionally.
I hope it helps and generates ideas for more secure and effective jigs.