It's a feature that, while not critical to tying a great fly, some tyers would find highly useful. Takes "rear hook access" from excellent to near unlimited. A good heads-up for anyone considering purchasing a Jvice.
Of course, many simple, non-rotary vises permit the same access.
The prior version was slightly different:
http://www.flyanglersonline.com/bb/a...3&d=1478734181