round rod 26 may extend through the body 25 and project therefrom to the rear a tension spring 29 may be hooked into the end of the rod 26 the other end whereof may be fixedly connected with the bearing block 180 by means of a holding bolt 30 the spring 29 insures that the round rods 26 and the yoke 24 are always brought into the position indicated in fig7 i e rotated counterclockwise about axle 230 in fig8 wherein the rods 26 occupy their upper terminal position the saw assembly 130 which moves freely on the rods 26 is normally held by the force of gravity in a left hand terminal position wherein the saw housing to be described below abuts against the frontal sides 25 a of the sleeve like bearing bodies 25 in the position shown in fig7 the saw assembly 13 is in its right hand terminal position in which it must be held by manual actuation with a handle 31 it is seen in fig9 that the saw housing 32 equipped with the manual handle 31 may comprise a pair of cylindrically shaped longitudinal guide passages 33 and 34 the internal diameter whereof may be coordinated with the outer diameter of the round rods 26 to slidingly receive the latter end sections of each of the longitudinal passages 33 34 may be provided with low friction guide.