I love how everything 'old' is new again, I have a horizontal clamp very similar to this application that has been handy for working with small parts over the years. I don't know how old it is, but the phone number has 'words' in it... so it's back a ways. It came to me from my Great-Uncle out in Shelbyville, IL about 25 years ago. I screw it down to the bench wherever and whenever needed, otherwise it lives in it's box.
The clamp is surprisingly strong for it's size.
Those kliss clamps would come in handy if working on a lot of doors, or other big bits that need to be worked on edge. If you are a contractor finishing a house, I be they are very handy and portable.