If you actually have SSSS on your boarding pass and you manage to get through security without the secondary screening, don't jump for joy. You might get sent back from the gate. Instead you should ask for a "signoff" that you got the secondary. You can ask for a secondary itself in subtle ways such as by keeping your shoes or heavy jacket on.

What does a "signoff" for secondary look like? A punched hole of a particular shape? A specific squiggle made by a marker of a specific color?

If the airline doesn't mark your boarding pass for SSSS and you are suddenly sent back, you may hold the airline liable for inconvenience if you don't get on the flight.

Travel tips:
http://members.aol.com/ajaynejr/travel.htm