I put A-1 on my pork chops. Everyone knows you're supposed to use Heinz 51. But I can't afford both So I eat more beef as a rule anyway, so I settle on A-1. So as it seems with the OP when he really needs a ND.
On the other hand, if he shoots lots of lakes, inlets, and other water bodies and wants to see the fish below the surface in his prints and forgot to bring the polarizer when he shot it, then he uses it on his enlarger so the fish will print, instead of the glare off the lake.
Two perfetly viable answers. There aren't any others.