PowerBreak is a tiny extension that allows developers and anyone else who uses Macsbug to drop into the debugger as though they had hit the programmer's key available on other Macs. It was created because I recently bought a PowerBook 145 and found that the only way to drop into the debugger was to stick a small object into this little cavity on the back (like the way you eject floppies from a disfunctional drive). What a pain! Hence, PowerBreak :P (But it can be used on non-porta-macs too!)
Install PowerBreak by simply dragging its icon into the Extensions folder in your System folder (if you use System 7.xx) or just into the System folder itself (if you do not).
To drop into the debugger, simply press the Control and Escape keys simultaneously. You should see the statement 'This is a PowerBreak...' and the familiar debugger screen.