I made this spring fuller out of a scrap car spring I found. It amazing how much more I have running through my head now that I have one. This little owl shaped opener is the first thing I made with it.

Tbh i dont know how u did that  can u explain?? I think i get how the fuller works but how is it useful?

I don't know if U can explain; but Thomas Powers can.  Look below the ring on the handle section; see the symmetrical indents made with the fuller? Quite difficult to do single handedly with separate top and bottom swages.  Now there are a lot of cases where you want matching indents---it's a handy way to delineate the blade/tang transitions on knives and swords for instance. or in making leaves. A variation is used to put fullers in blades. Sculpture work, tools, etc. 

I find I tend to design for the tools I own and my swing arm fuller is one of the most heavily used tools in my shop!

Thanks Thomas. This has quickly became my favorite tool. The same effect can be done with a striker and top and bottom fullers but this is much easier for a single man operation as my self. I have used it to draw out quills on feathers and even collapse pipe down for peppers and candle holders with lighter taps. 

Thomas, can you please show me your swing arm fuller or send me the link if you already put it out. It sounds interesting.

I'll try to get one posted in the next couple of days

The moving bar was made from a straightened piece of pickup coil spring with a flat hammered into it for the bolt hole, Normalized.

The body was a piece of scrap I found, only thing I did was to remove about 1/2 the upright setion on top so the swing arm would be aligned over the bottom section

Spring is a die spring I got from Ptree at Quad-State.

Bolt is a cheap one from the hardware store, I tighten the bolt till the spring will just stay up so I can lift it by taping the left end down or using the extension of the right end.

Note I have used this a LOT and replaced the swing arm bar a couple of times and the bolt 4? Times---some students can't seem to get that if you don't hit the swing arm right over the workpiece you are stressing the bolt.