If the device includes a rubber boot, then it is not necessary to use a shim in the cradle. If the shim is in the cradle, you must remove it first, before inserting the device in the charging slot.
If the device does not include a rubber boot, then it is necessary to use a shim in the cradle. If the shim is not in the cradle, it must be inserted first, before inserting the device in the charging slot.