The unit cell visualizer may be run as a stand-alone program or it can be opened from within JSV, whereby the cell dimensions of the presently loaded structure are automatically used. The main purpose of this modul is to show the directional relations between vectors [uvw] and (hkl). In the cubic system the vectors  and (111) for example point in the same direction (enclosed angle=0). For other system, however, it becomes more difficult to imagine those relationships.
You may specify up to ten different vectors (leave spaces between the indices!). Then both the [uvw] and the (hkl) with the same indices are drawn if you check the checkbox of that vector and click "apply changes".
Normally you are in the rotation mode, which means that mouse drags result in the rotation of the cell around the x,y,z axes. (use left & right mouse button!)
When you check the checkbox zoom & shift dragging with the left mouse button pressed results in zooming the cell and dragging with the right mouse button pressed results in moving the cell around.
When you select "unit length" then both [uvw] and (hkl) will be shown with the same length, thus making their directional relations better visible.
On the left in the display area the vectors are listed with their serial number and length. If you want to measure the angle between two vectors put their serial numbers in the text field "measure angle" and click "apply changes".