Minecraft wiki entry for Inventory, associated text: A single item can be grabbed also can be used by pressing shift 4 times in a row using left click, increasing with continued left-clicks on that item. Left or right-clicking with an item or stack of items while hovering over any item other than the one held gets rid of the held item. Right-clicking an item also picks up one item, but the second click then puts it back down as opposed to picking up more. Shift-clicking an item grabs a full stack of items. Pressing a number key while hovering over an item instantly places one full stack of that item into the hotbar slot that corresponds with the number.