An old hollow core door makes a perfect workbench that is both lightweight and easy to store.
Start by laying the door on the floor and position two collapsible sawhorses upside down on top of it a foot or so from each end.
Screw the sawhorses to the solid wood frame that runs around the outer edge of the door with 1¼” screws. Turn it upright, and it’s ready for use.
To store the workbench, flip it over and fold up the collapsible legs.
Store it flat against a wall.