I've been reading Patrick O'Brian lately. I bacame curious, what is hard tack. I know it was a staple on long voyages in the high era of the British sailing navy, according to Patrick O. <smile>

So here is how to make it. . . ripped from somewhere in net land:

Take white flour and mix with just enough water to
make a stiff paste. Knead well and make rectangular cakes about one-half
inch thick. You can poke holes in with a fork if you like. Bake until
light brown. Turn down oven heat to about two hundred degrees and
dessicate until they're hard enough to beat a hole in the wall with.

No I haven't tried this. . .yet.

According to my recent search this is similar at least in the first steps to making flour glue. Go figure.