Palette knife - lock rotation or contrain to thin vertical and horizontal lines

[pepperstreet]

Hello artists,
does someone know a way to achieve a thin vertical or horizontal line? How to rotate and move the knife "on the edge"? I tried everything, but I can't get a proper setting. I have to admit, that my wacon tablet/pen does support tilt, but not the pen rotation. But I see no problem with it... if I would use a mouse, It should also be possible to achieve this kind of constraint. My first thought was the "lock rotation" setting. I tried different values, but I can't get the desired result. Simply reducing the knife size is no option, I want a large knife that I move in the direction of the handle. This constraint should work for vertical and horizontal strokes. Hope this makes sense

Any tips? Did I miss something?
Thanks in advance.