release of a cart unless the proper amount of money is inserted into the control unit 52 fig2 illustrates carts properly received on the island 10 the carts first wheels are received within the channel 24 with their supporting axle 36 riding in the slot 28 in order to preclude capture of a cart with it oriented in a direction opposite that of the desired nesting direction that is with its second wheel 42 captured in the channel 24 anti reversing means are provided as seen in fig2 through 6 the anti reversing means can comprise a laterally extending member or tab 54 the tab 54 extends from the second side of the cart 14 and is disposed proximate the second wheel 42 in a preferred embodiment the tab 54 is affixed at one end thereof to the axle 38 supporting the second wheel 42 a remote end 56 extends to a position wherein if insertion of the cart 14 onto the island 10 in a reverse orientation is attempted the tab 54 will engage the entry end of the channel 24 at a location spaced from the entrance to the slot 28 entry of the second wheel 42 of a cart 14 into the channel 24 is thereby precluded in order to insure engagement of the end of the channel 24 by the tab 54 the tab 54 should extend from the axle 38 at least to a plane defined by an inwardly facing surface 58 of the second wheel 42 as can be seen the end of the tab 54 remote from the axle 38 can be positioned outside the periphery of the second wheel 42 in order to minimize the chances of damage to either.