The plastic case completely encloses the glass ampoule (with the dot on the amp facing out), holding it in place so that it can be broken with a simple 'snap'. 

The snapper can then be easily opened and the ampoule can be removed, or it can be locked in the open position (by means of a clip on the back) and contents of the ampoule can be drawn up in situ. 

When using ampoules that have been scored to make opening easier, you must place the ampoule in the snapper correctly, otherwise the amp may shatter inside the device. 

ALWAYS HAVE THE BLUE DOT FACING OUT.