A technique for selectively configuring a case of a handheld device to shield an antenna from receiving or transmitting wireless signals is disclosed. The technique includes moving a blocking element on the case between a first position and a second position. The blocking element is a physical structure that is rotatable, slidable, or removable to switch between the first position and the second position. In response to moving the blocking element to the first position, the blocking element blocks wireless signals received or transmitted by the antenna of the handheld device. In response to moving the blocking element to the second position, wireless signals can be received or transmitted through the case by the antenna.