Abstract: A sheath which permits the user to adjust the degree of retentional engagement of the knife within the sheath. The sheath is provided with a simple, adjustable, latch mechanism engaging the knife to prevent their accidental disengagement. The latch mechanism is substantially received within the sheath.

Abstract: There is disclosed an impact device for operation from a source of alternating power and with at least striking member adapted to be electromagnetically actuated to impact against an opposing surface. An electrical gate under the control of a switching circuit and at a given point in time and for a given time duration connects a source of alternating power to the electromagnetic striking member. A source of gate control pulses for rendering the electrical gate conductive and non-conductive is connected through the switching circuit under the direction of a switch control circuit to the electrical gate for selecting which of the gate control pulses are to be connected to the electrical gate.