The German term for Rafters is Sparren. And I believe the German technique, prior to saws, was to stand on the rafter, which was set very low to the ground or even on it, and use the long handled Breitbeil (broad axe) which has a handle as long as a felling axe or even longer. This as opposed to the short handled Breitbeil, which is the goosewing we are all familiar with. You would chop down below your feet with this axe, sweeping along the timber to square it off. It is actually quite easy to square off a timber with this axe without snapping any lines at all, as the motion follows very naturally in a straight line and allows you to sight yourself as you go. And here I think that the act of standing on the timber helps keep it from bouncing
This longer-handled axe has a heavy profile similar to a goosewing, having the lower beard but not the upward sweep. The bit is around 8 inches or so, as opposed to the 12 inch or more size of a goosewing bit. Its own weight is used to do all the work, rather than a forceful swing.