secondary (i.e. additional/enhanced) screening is what the tsa does to you when....

• you have an unresolved alarm upon going thru the wtmd and "win" a full body pat down (with or without an explosives test swab of your palms and/or shoes)
• there is an item in your bag that the tso cannot determine what it is at the x-ray and they must do a bag search
• either or both of the above "when they feel like it" to justify it being totally random*

for the tsa, just make sure that you abide by the liquid and shoe nonsense rules and you'll be fine and keep in mind that the tsa cannot be looking thru your passport, wallet and/or cell phone and/or recording any of the information in them for that matter-even tho they think they can, they cannot-customs otoh, can do it but not the tsa.

for u.s. customs, it all depends upon your nationality as to what if anything you are asked. just be up front with nothing to hide and you'll be fine.


*if you have a muslim sounding name, appear (n.b. appear) to be "brown skinned and/or are wearing a turban, it is considered a random selection