I used these on my last build and they will be a "go to" item for me in the shop from now on. I bought about 36 on sale.
The nice thing is that the mod is reversible, so when you are doing a build, make up the "Jimmie Clamps" and they are very useful. When you finish, reverse the mod and you have several dozen clamps for routine shop use ... I have always had a couple of spring clamps around, but having dozens of the larger ones really comes in handy and I use them generally a lot more, as they are sitting right there.
Brian