Well..........I know of three different ones in service by various members here. Bitzenburg, Jo Jan, and Bohning's tower jig.

I personally went the "frugal" route and bought a Grayling jig - it's plastic, rather than metal, but it works like a hot darn. I'm careful with it and treat it like plastic - not metal, as I said it works just fine.

Hopefully some others will add their 2 cents worth.