cracks in old pine flooring
Just returned from my favorite local hardwood flooring haunt (I must have NO life!)
Carpetman is, of course, correct--best to ask your flooring experts--but when I asked mine this question they recommended "Bruce Acrylic Filler."
I myself have a whole floor I'm working on--different story than what you've got going, I believe. For me they recommend troweling in Latex wood filler over the entire floor (after the coarse sanding). This comes in gallons. But I thought I'd share this too in case you have more going on.
k2 in CO