@Peter, the point is to get achieve automatic rotation: the oldest flour (on the bottom) gets used first. Otherwise, refilling needs a third bucket, whereby you dump the dregs into it, then fill the old container with the new stuff, then put the dregs on top. For people who are too lazy to rotate, the bottom stuff will get pretty stale and end up affecting the flavour and sanitization of the newer stuff on top. I used to work in a bulk food store, and this kind of rotation was a PITA, messy part of the job. Most modern bulk stores are equipped "first-in, first-out" dispensers, as in those the OP is looking for. The oldest stuff always gets sold first (from the bottom).

@Peter, the point is to get automatic rotation: the oldest flour (on the bottom) gets used first. Otherwise, refilling needs a third bucket, whereby you dump the dregs into it, then fill the old container with the new stuff, then put the dregs on top. For people who are too lazy to rotate, the bottom stuff will get pretty stale and end up affecting the flavour and sanitization of the newer stuff on top. I used to work in a bulk food store, and this kind of rotation was a PITA, messy part of the job. Most modern bulk stores are equipped "first-in, first-out" dispensers, as in those the OP is looking for. The oldest stuff always gets sold first (from the bottom).