An incredibly useful feature of the Finder in Mac OS versions 8 and 9 (and coming to Mac OS X in summer 2002), spring-loaded folders allow users to descend into the folder hierarchy without manually opening folders. Here's how they work:

  1. Drag the object over the first folder (either a hard disk, a folder on the Desktop, or a subfolder of an already-open folder.
  2. Hold it there for a second, or press SPACE.
  3. The folder flashes and opens. Repeat the process with another subfolder, or drop it into this window.
While a bit complicated to explain, the procedure is very helpful once you get the hang of it. Windows has implemented a very similar method when dragging an item onto the Start Menu: drag over "Start", hold, drag over "Programs", hold, drag over folder name, hold, drop into folder. This works in Windows 98 or later versions.