pivot control point and lines: ctrl = snap hard to face vertices and grid
grid density controls: shift = change density of both axes synchronously, ctrl = power of two grid
scale lines: shift = scale axes synchronously, ctrl = snap hard to vertices
alt + m1 on grid = skew texture (is possible alright in BP and Valve220 map formats, not in AP); ctrl = snap hard to edges
texture move: shift = only move along the axis with the biggest move, ctrl = snap grid lines hard to vertices and pivot
rotate: shift = rotate with step of 15 degrees, ctrl = snap hard to edges
