Many newer tool boxes have a little lever that
you can push down that lets the drawer pull all the way out.
With older tool boxes, a flat spring on the H shaped slide grabs a protrusion or rivet on the drawer. You have to slide another flat spring between the first flat spring and the protrusion to let the spring slide over the protrusion.
The typical tool box drawer with even medium weight is pretty wobbly outside the box and is much more likely to get damaged.
Sears has smaller tool boxes with 2 or 3 drawers and a carrying handle in the middle of the top lid. I would suggest them for easy portability even if you have to buy some duplicate tools.