An improved method and apparatus for selection of vendible products provides designated product reference areas at a refrigerated double glass front vending machine for making viewable product selections thereon by applying a light tap at its outer glass pane and sensing the tap location by three or more spaced apart resilient members each having its first portion attached at the inner glass pane. The resilient member's second portion suspends an inertia mass that reciprocates at a predetermined rate due to the inertia mass weight and the resiliency of the suspending member. A sensor senses the reciprocating movement in response to the light tap. The location of the tap is determined by measuring the arrival time of each predetermined signal produced by the first resonating alternation of its attached resiliently suspended inertia mass during the first rearward movement of the inner glass pane.