A pager is a map of your desktop.  As maps go, it shows not only the visible
part (your current viewport), but, if you are so configured, also the parts
that extend beyond the sides of your screen.  Also, if you have more than one
workspace, the pager will follow you to where you are, or optionally show all
workspaces at once.  Of course you can select viewports and windows, and also
move or raise/lower the latter.

Activation

Versions are not intercompatible with older ones!  Make sure you reload both
the lisp module and the external program, for example by restarting sawfish.

In your resource file you could add something like:

(require 'sawfish.wm.ext.pager)
(add-hook 'after-initialization-hook pager t)

