Question:
This happened to me...... Don't let it happen to you!!!!
Middle of the night, dark drop yard (sorta) and a long day. All I was really thinking about was dropping my loaded trailor, picking up an empty and finding a safe place to park for the night.
Got the trailor in the parking spot, cranked down the leg(s), looked under the trailor and realized something wasn't right.
I've learned to trust that little voice telling me something isn't right....
The driver's side leg was on the ground but the passenger side was still up!!!! Very carefully, I started checking around and found that the bolt holding the connecting rod between the legs had rusted through and finally broken. Fortunately, I carry a supply of different sized bolts, washers and nuts so I was able to fix the problem.
The potential disaster, I'll leave to your imagination as to what could have happened.
The lesson learned?? Never be too sure. Always double check that both legs have come down and are on the ground.
Too many times it's easy to fall into the trap of just watching the driver's side leg contact the ground and assuming the passenger side is down as well. Especially when you're tired..... I ride for those who can't! POW/MIA - You are NOT forgotten!!
Lead, Follow or get out of my way!!!

Answer:

And dont forget to check to make sure both legs are all the way up when hooking to a trailer.
Answer:
I always check the set. Learned it in school.