Mk IV Heavy Duty 5" Fret Saw with Lever Tension clamps. 

Gives you more tension than the regular 5" Fret Saw but is a heavier saw.

The Lever can detension the blade quickly and allow quick and easy blade changes. Truly the ultimate in saws. You can saw the base-line of dovetails. 

Please check out Christopher Schwarz's review here, a great source of info on this amazing saw,   http://www.popularwoodworking.com/woodworking-blogs/chris-schwarz-blog/knew-concepts-fretsaws-approach-perfection