Do you mean to grab a region of the screen for a screenshot or are you talking about the NNTP usenet tool called grabit
, which is part of KDE, can grab the entire screen, a region of the screen, or a specific window. It's my preferred screenshot tool. If your distro has repos, it should be in them.
Gnome also has a screenshot tool, but I haven't used it in ages.
It it's the usenet tool, there's this
, but I've never used it.