A surgical instrument, comprising: an end effector, including: an ultrasonic blade, and a clamp arm configured to move relative to the ultrasonic blade from an opened position toward an intermediate position and a closed position, wherein the ultrasonic blade and the clamp arm are configured to receive tissue in the opened position, wherein the clamp arm is configured to clamp tissue against the ultrasonic blade in the closed position, and wherein the clamp arm is offset from the ultrasonic blade to define a predetermined gap in the intermediate position between the opened position and the closed position; a shaft assembly projecting proximally from the end effector and including an acoustic waveguide operatively connected to the ultrasonic blade, wherein the acoustic waveguide is configured to connect to an ultrasonic transducer; a body projecting proximally from the shaft assembly; a clamp arm actuator operatively connected to the clamp arm and configured to selectively move relative to the body from an opened configuration to a closed configuration to thereby direct the clamp arm respectively from the opened position toward the intermediate position and the closed position; characterised by a spacer operatively connected to the clamp arm and configured to inhibit movement of the clamp arm from the intermediate position toward the closed position for maintaining at least the predetermined gap between the clamp arm and the ultrasonic blade, wherein the spacer includes an adjuster configured to manipulate the spacer from an unactuated position to an actuated position, wherein the spacer further includes a blocker configured to inhibit movement of the clamp arm actuator towards the body with the spacer in the actuated position. an end effector, including: an ultrasonic blade, and a clamp arm configured to move relative to the ultrasonic blade from an opened position toward an intermediate position and a closed position, wherein the ultrasonic blade and the clamp arm are configured to receive tissue in the opened position, wherein the clamp arm is configured to clamp tissue against the ultrasonic blade in the closed position, and wherein the clamp arm is offset from the ultrasonic blade to define a predetermined gap in the intermediate position between the opened position and the closed position; an ultrasonic blade, and a clamp arm configured to move relative to the ultrasonic blade from an opened position toward an intermediate position and a closed position, wherein the ultrasonic blade and the clamp arm are configured to receive tissue in the opened position, wherein the clamp arm is configured to clamp tissue against the ultrasonic blade in the closed position, and wherein the clamp arm is offset from the ultrasonic blade to define a predetermined gap in the intermediate position between the opened position and the closed position; a shaft assembly projecting proximally from the end effector and including an acoustic waveguide operatively connected to the ultrasonic blade, wherein the acoustic waveguide is configured to connect to an ultrasonic transducer; a body projecting proximally from the shaft assembly; a clamp arm actuator operatively connected to the clamp arm and configured to selectively move relative to the body from an opened configuration to a closed configuration to thereby direct the clamp arm respectively from the opened position toward the intermediate position and the closed position; characterised by a spacer operatively connected to the clamp arm and configured to inhibit movement of the clamp arm from the intermediate position toward the closed position for maintaining at least the predetermined gap between the clamp arm and the ultrasonic blade, wherein the spacer includes an adjuster configured to manipulate the spacer from an unactuated position to an actuated position, wherein the spacer further includes a blocker configured to inhibit movement of the clamp arm actuator towards the body with the spacer in the actuated position.