Abstract: A dual-cam device is described configured to be engaged with a rail and a stopper for clamping at least one object. The dual cam device comprises a jaw; a body; a member connecting the jaw and the body wherein the member has a member-base configured to associate with and slide on the rail; and a lever pivotally connected to the member, wherein the lever has a first cam and a second cam and wherein the lever is configured to be tilted from an open position to a clamp position and vice versa. During tilting the lever from an open position to a clamp position in which the object is clamped, the first cam causes the dual cam device to secure emplacement position of the dual cam device to the rail and then the second cam causes the dual cam device to press and clamp the object by the jaw against the stopper. It is further described a clamping apparatus that comprises at least one dual cam device; at least one rail having a channel; and at least one stopper.

Abstract: A combination square for usage with a grooved blade, comprising: a straight component having a first straight edge and a second straight edge perpendicular to the first straight edge; an angled component having a third straight edge and an angled edge; a marked scale comprising degrees; a marker, wherein the square is configured to allow indication by the marker of angles on the scale; a slot configured to allow accommodating the blade; and a locking screw configured to allow clamping the combination square onto the blade at a desired position along the blade; wherein the angled component is rotatably connected to the straight component; and the square is further configured to allow measuring a center of a circle coupled to the second straight edge and the angled edge at a second end of range of motion of the rotation by the straight component relative to the angled component.

Abstract: A combination square for usage with a grooved blade, comprising: a straight component having a first straight edge and a second straight edge perpendicular to the first straight edge; an angled component having a third straight edge and an angled edge; a marked scale comprising degrees; a marker, wherein the square is configured to allow indication by the marker of angles on the scale; a slot configured to allow accommodating the blade; and a locking screw configured to allow clamping the combination square onto the blade at a desired position along the blade; wherein the angled component is rotatably connected to the straight component; and the square is further configured to allow measuring a center of a circle coupled to the second straight edge and the angled edge at a second end of range of motion of the rotation by the straight component relative to the angled component.