Most holdfasts do a fine job of clamping the work when it’s 2” or less off the benchtop. But when the work is higher than that, the tool might balk at the task.
I used to think that holdfasts were useful only for low-lying applications, such as holding battens to the benchtop. But if you’ve ever built drawers, you’ve probably longed for a holdfast that would secure the drawer so you could level the joints at the corners with ease.
https://player.vimeo.com/video/183533103
Crucible Holdfast from Christopher Schwarz on Vimeo.
The Crucible Iron Holdfast is designed to work as much as 8” off the benchtop, thanks to its shaft, which is untapered, rough and a close fit to its hole in the benchtop.
You might not think you need a holdfast that can work 8” off the benchtop. But wait until you need to clamp down a drawer from a dresser. Or a table apron. Or a brick-moulded apron for a game table.
— Christopher Schwarz