Finding and utilizing both cover and concealment are fundamental lessons for any war fighter, and both are pounded into the brains of Marines through recruit training and the School of Infantry, but snipers take these fundamental lessons to the next level. Traditionally speaking, cover is a term used to describe things you can hide behind for protection from inbound rounds, whereas concealment is a term used to describe things you can hide behind that will only inhibit detection. A large boulder can offer both cover and concealment, for instance, whereas tall grass offers concealment without the benefit of cover.

In a firefight, understanding the difference between these concepts is a matter of life or death, but often, the mission parameters snipers run across demand movement across swaths of land with very little cover. In these environments, snipers must utilize different concealment techniques (often layered into what they refer to as “screens”) so effectively that they go completely undetected, even when enemy troops are standing right on top of them. Without the benefit of cover, it’s just the shroud of concealment that keeps these war fighters alive, and as such, Marine Snipers devote a great deal of time and energy to honing their concealment skills.

This fact of warfare was put to the test recently, when Business Insider sent a journalist to observe Marine Scout Snipers as they trained in Quantico, Virginia. At the onset of the training schedule, the Scout Sniper instructor (who was not named) demonstrated the value of concealment by inviting the visiting journalist, a dozen Marine sniper students, and a handful of Army Rangers to attempt to find him as he closed with their observation post.

“I’m going to use the terrain to my advantage,” the instructor told said at the outset of the training revolution. “You can see there is a hill back there, I don’t want to go over the very top of the hill. I want to come around the side of the hill, follow the low, dead space down, and then come up from behind into my position, always maintaining that low profile, low silhouette.”