A hinge includes a base frame unit and two rotatable axle units. The base frame unit includes a base seat and a protective cover. The base seat has two guideways having upper and lower segments, and two shaft sliding slots. The protective cover has a base wall and two pivot pins. Each axle unit rotatably extends through the base seat, and includes a hinge shaft rotatably extending through the shaft sliding slot, a first rotary member non-rotatably fitted to the hinge shaft, a second rotary member connected with the first rotary member, and a support bracket non-rotatably fitted to the hinge shaft. The first rotary member has a guide key slidably engaged in the guideway. The second rotary member is pivoted to the pivot pin and has an engaging hole for receiving the guide key.