This is just speculation on my part, but a glue such as cyanoacrylate would be extremely useful for attaching a handle to an improvised tool or weapon.

I guess it's lighter than duct-tape and concealable too. I know the hacksaw blades would be useless as anything but weapons, so it's probable that there's an inmate who's now stuck with a surplus of handles and no blades. Worse yet, he could also have a bunch of late drug orders.

In addition to the variety of suggestions so far:

You can mend things with it.

I dunno, but recently when buying some at the local Walmart, an alert went off and they carded me to see if I was over 18. The guy at the checkout didn't know why but he speculated sniffing of some kind.

In a pinch, you can use it as an alternative to stitches.

You can also sniff glue to get high, cheap drugs. Although it wouldn't have to be "super"-glue.