Locks can only be opened by you. NO TSA LOCKS even though TSA says you can. But would you want TSA able to access your firearms?
They can be keyed or combo, but only you can have access to it
https://www.tsa.gov/travel/transporting-firearms-and-ammunitionFirearms
When traveling, comply with the laws concerning possession of firearms as they vary by local, state and international governments.
If you are traveling internationally with a firearm in checked baggage, please check the U.S. Customs and Border Protection website for information and requirements prior to travel.
Declare each firearm each time you present it for transport as checked baggage. Ask your airline about limitations or fees that may apply.
Firearms must be unloaded and locked in a hard-sided container and transported as checked baggage only. As defined by 49 CFR 1540.5 a loaded firearm has a live round of ammunition, or any component thereof, in the chamber or cylinder or in a magazine inserted in the firearm.
Only the passenger should retain the key or combination to the lock unless TSA personnel request the key to open the firearm container to ensure compliance with TSA regulations. You may use any brand or type of lock to secure your firearm case, including TSA-recognized locks.
Bringing an unloaded firearm with accessible ammunition to the security checkpoint carries the same civil penalty/fine as bringing a loaded firearm to the checkpoint. You may find information on civil penalties at the Civil Enforcement page.
Firearm parts, including magazines, clips, bolts and firing pins, are prohibited in carry-on baggage, but may be transported in checked baggage.
Replica firearms, including firearm replicas that are toys, may be transported in checked baggage only.
Rifle scopes are permitted in carry-on and checked baggage.