The Collapse Cross Tangent Tangent V command allows you to set the cross tangent tangency values of your XirusCAD object at the selected point(s) to 0 in the v direction.
You can call the Collapse Cross Tangent Tangent V command from the XirusCAD menu, from the XirusCAD Toolbar or from the command line. Select the points on your XirusCAD surface in the v direction. The cross tangent tangency of these points will be collapsed in the v direction. This means that the cross tangent values at those points will be set to 0 in the v direction.
In the video, the Collapse Cross Tangent Tangent V command is found under a different XirusCAD menu item.