At McDonald`s, the customer orders a hamburger, the server gets one from the rack, the hamburger maker keeps an eye on the rack and makes new burgers when the number gets too low. The manager orders more ground beef when the maker`s inventory gets too low. In effect, the customer` purchase triggers the pull of materials through the system... In a push system, the caterer estimates how many hamburgers are likely to be ordered in any given week. He/she can then figure out roughly how many ground beef need to be ordered in a certain week in advance...