Abstract: A driller retaining device able to be positioned with well horizontality and verticality includes a hollow outer sleeve having two end, one is a working end and the other being an assembly end; an inner wall of the assembly end being formed with a plurality of axial sliding tracks; an inner hollow cylinder arranged within the sleeve; two ends of the inner hollow cylinder being an machine end and an assembly end; an outer wall of the inner hollow cylinder having at least one sliding block which is arranged corresponding to the axial sliding groove. In in assembly, the inner hollow cylinder is combined to the driller; then the assembly end of the inner hollow cylinder is assembled to the assembly end of the outer sleeve; and at the same time, the sliding block of the inner hollow cylinder is assembled into the axial sliding groove of the outer sleeve.

Abstract: A detachable bolt includes a bolt body being a round bar and having an inner end and an outer end; a periphery of the inner end being formed with at least one screw section with threads thereon and at least one circular section; each circular section having a smooth surface with a plurality of protrusions. The outer end of the bolt may be a structure like that of the inner end, or may have threads thereon, or may be smooth, or may be sleeved by a sleeve. In detaching process, other than the gluing material in the hole will break, the object to be retained and the retaining wall will not be destroyed. The bolt body can be removed from the object and the wall easily without great forces applied thereto. Furthermore, the wall and the object to be retained can be restored to the original outlook easily.

Abstract: A high precision positioning ruler with an indication pen includes a ruler body having a longitudinal penetrating hole; a scale for indication of lengths being formed on a surface of the ruler body; a positioning unit being slidable along the longitudinal penetrating hole for being positioned to a point of the scale; the positioning unit having an pen for drawing points or lines to indicate lengths to be measured; a leveler and a verticality mater being installed on the ruler body for controlling the ruler to be positioned horizontally or vertically. In use of the ruler, the ruler resisted against a measuring surface; for horizontal measurement, the user views the leveler to control the horizontalness of the ruler; then the positioning unit being moved along the longitudinal penetrating hole to a desired length and then the pen is used to indicate the point.