I’ll admit that I’m staggered by how a lot of writers absorb hundreds of little details of how trained soldiers/detectives will use little tricks to survive, observe a room, or follow patterns of criminals. Once long back, those little things like leaving a bit of pencil graphite in a door hinge to denote intruders (or, in Better Call Saul’s case, placing a carbon sheet under the doormat) were extremely rare to hear about. I don’t even know who you’d ask without ending up on a list.