Still Life can't use Cutters on boxes from inventory

I have the two loose boxes in the junkyard lined up properly (I think)and Gus walking across them ok, but I can't pick up the cutters from the inventory and use them. The inventory goes dark when I click the closed fist icon at the top. Is this a glitch or am I missing something fundamental? I have checked the instructions several times and it seems I am doing this right.

Let's ascertain if this is a gameplay problem or a true glitch. If the Hints forum doesn't help, we can continue this thread later and try to determine if it's a glitch.