A tube or cable jacket slitting or cutting tool comprising: first and second opposite tool portions (22a, 22b), each tool portion (22a, 22b) including a common hinged portion at a first end for engaging the first and second opposite tool portions (22a, 22b), the first and second opposite tool portions (22a, 22b) being foldable about the hinged portion between an open position and a closed, folded-together position, each of the first and second opposite tool portions (22a, 22b) having a length, width, and height, with the length extending in the direction from the hinged portion at the one end to a second end (26a, 26b) opposite the hinge, the width extending in the direction perpendicular to the length, and the height extending in the direction perpendicular to the length and width, the first and second opposite tool portions (22a, 22b) meeting along a plane comprising the length and width when in the closed position; at least one concave surface (31a, 31b, 32a, 32b, 33a, 33b, 34a, 34b, 35a, 35b, 36a, 36b) extending across the width of at least one of the first and second tool portions (22a, 22b), the at least one concave surface forming an opening, when the first and second opposite tool portions (22a, 22b) are in the closed position, through which a tube or cable may be slid with respect to the tool; a blade extending inward into the opening formed by the at least one concave surface (31a, 31b, 32a, 32b, 33a, 33b, 34a, 34b, 35a, 35b, 36a, 36b) for slitting or cutting a depth of the tube or cable jacket as it is moved with respect to the tool; characterised in that, a hinge pivot axis in the hinged portion extending in a direction substantially in the direction of the width and at an acute angle to either the plane or to the longitudinal axis of the tube or cable in the opening formed by the at least one concave surface, wherein when the first and second opposite tool portions (22a, 22b) are folded to the closed position with the tube or cable in the opening, the blade cuts into the tube or cable outer jacket and movement of the tube or cable with respect to the tool in one direction to slit or cut the tube or cable jacket with the blade causes the first and second opposite tool portions (22a, 22b) to be urged toward each other. first and second opposite tool portions (22a, 22b), each tool portion (22a, 22b) including a common hinged portion at a first end for engaging the first and second opposite tool portions (22a, 22b), the first and second opposite tool portions (22a, 22b) being foldable about the hinged portion between an open position and a closed, folded-together position, each of the first and second opposite tool portions (22a, 22b) having a length, width, and height, with the length extending in the direction from the hinged portion at the one end to a second end (26a, 26b) opposite the hinge, the width extending in the direction perpendicular to the length, and the height extending in the direction perpendicular to the length and width, the first and second opposite tool portions (22a, 22b) meeting along a plane comprising the length and width when in the closed position; at least one concave surface (31a, 31b, 32a, 32b, 33a, 33b, 34a, 34b, 35a, 35b, 36a, 36b) extending across the width of at least one of the first and second tool portions (22a, 22b), the at least one concave surface forming an opening, when the first and second opposite tool portions (22a, 22b) are in the closed position, through which a tube or cable may be slid with respect to the tool; a blade extending inward into the opening formed by the at least one concave surface (31a, 31b, 32a, 32b, 33a, 33b, 34a, 34b, 35a, 35b, 36a, 36b) for slitting or cutting a depth of the tube or cable jacket as it is moved with respect to the tool; characterised in that, a hinge pivot axis in the hinged portion extending in a direction substantially in the direction of the width and at an acute angle to either the plane or to the longitudinal axis of the tube or cable in the opening formed by the at least one concave surface, wherein when the first and second opposite tool portions (22a, 22b) are folded to the closed position with the tube or cable in the opening, the blade cuts into the tube or cable outer jacket and movement of the tube or cable with respect to the tool in one direction to slit or cut the tube or cable jacket with the blade causes the first and second opposite tool portions (22a, 22b) to be urged toward each other.