Opportunistically employing everyday objects as tangibles provides a promising avenue for wider adoption of Tangible User Interfaces. However, the potential double purpose of these objects both as tangibles and for their originally intended purpose makes opportunistic tangible interaction susceptible to the Midas Touch effect. Explicit clutching mechanisms that control the activation and deactivation of these tangibles offer a solution to this problem, but the optimal choice of clutching method remains unclear in the context of opportunistic tangibles on interactive tabletops. This paper investigates suitable clutching mechanisms through a controlled user study (n=24), comparing four different clutching methods: Activation- and Address Gestures, Active Zones, and Pedal clutches. We analyze quantitative measures of user experience as well as qualitative feedback, identifying advantages and disadvantages and singling out Address- and Activation gestures as points of reference for future work.