a liquid transfer tool allows a nearly empty plastic bottle to be emptied into another bottle that is to be saved . shampoos and other liquid like perfume are very expensive and users of these products want to save every last drop in a bottle . the handy screw on caps include a mating portion that allows a user to screw both caps onto the bottles to be joined together for salvaging the fluid of the more empty bottle into the bottle that is more full through either a snap fit or male and female mating threads .