Alas, they are very inconsistent. There appear to be some significant training problems.
Several years ago I drove a car down to San Diego for my son to use while in college. I was flying home, that is, one way and not a round trip, as an unaccompanied male. That appeared sufficient to put a SSSS on my boarding pass. At Gate 1 at San Diego International, I was pulled aside for the secondary screening. Shoes and belt in the bin, empty pockets, stand on the painted footprints, arms out. The usual drill, while the rest of the passengers board the plane and wonder about the suspicious person.
There's a TSA agent in front of my going through my carry on bag, and another behind me with that big metal detector wand. Now, I've lost about 35 pounds from the previous year at this point in time, so my clothes are sort of loose. Sure enough, after holding "the position" for a little while with no belt, my pants start to slip. The agent in front of me shouts "Pull your pants up!", and I lower my arms towards my pants. The agent behind me hits my side, on the rib cage using the metal detector wand as a club, and shouts "Arms out!". My pants fall to the floor. Both agents start screaming, and I'm struck in the back with the metal detector wand. I don't dare move, as I've already been struck twice, and I don't know if one of the other agents in the area might have a weapon aimed at me.
Finally the agent in front of me says I can go, so I look around, see that nobody is ready to whack me again, pull up my pants, grab my shoes and bag and run for the plane in my socks. The ground crew has already removed the rear stairs, but the front stairs are still there and the door is open. (Gate 1 didn't have a jetway. It's an old school, walk on the field to the plane gate.). I left my belt at the gate with the TSA professionals.
If anyone wonders why I have a poor opinion of the TSA, this is the reason why.