What is my USE ??

[rudeawakening55]

This tool is marked JIFFY pat apld for  Outside measurement is 7 1/2" x 7" the top arm swivels 180 degrees & is threaded with a 45 degree swivel on arm. Inner arm can thread out 2 1/4". Have had this to several tool shows, but no luck in identifing it's use.  Would guess it's for carpentry.

[Branson]

This tool is marked JIFFY pat apld for  Outside measurement is 7 1/2" x 7" the top arm swivels 180 degrees & is threaded with a 45 degree swivel on arm. Inner arm can thread out 2 1/4". Have had this to several tool shows, but no luck in identifing it's use.  Would guess it's for carpentry.

Almost certainly for wood work.  Some kind of adjustable quick clamp, hence the "Jiffy" name.   Adjust the space with the threads, and it should cam into a locked position, kinda like vise-grip pliers.  The key-hole openings would let you attach it and take it off as needed. 

[BruceS]

I could use a couple dozen of those.    I'd use them to make adjustable shelves.

[keykeeper]

Reminds me of some type of metal brake, or a saw vise of some sort?