This skill governs the ability to hide from sight. With a successful BCS roll the character is completely hidden from someone not actively searching for the character. Someone using his/her Spot Hidden skill will have a chance to see the character hiding. The character hiding tries his/her Hide BCS roll, with a successful roll the number between the needed roll and the actual roll is subtracted from the BCS of the person trying to spot the hidden person. If the character fails his/her hide roll the number between the needed roll and the actual roll is added to the BCS of the person trying to spot the hiding person.
As an example: John was searching the ruins of a building, when he heard some people approaching. He panics and begins to run towards the back door. The approaching people hear John scrambling for the back door. They draw their weapon and enter the building. Once John reaches the back door he realizes that the door is bolted shut. With nowhere to run, John decides his best chance for survival is to hide. John has a hide skill of 12. Looking around he finds some debris to hide in. The GM has John roll his hiding skill. John rolls an 8, Success. Shortly after John hides the 2 people enter the back room. Taking a quick survey of the area they see nothing. One of the people decides he should take a closer look. He takes him time and looks around for anything or anyone. The GM rolls the persons Spot hidden roll at a 4(Johns Hide BCS was 12 he rolled an 8. 12-8=4, so the person gets a 4 penalty to his Spot hidden roll). His Spot Hidden skill is 15. He rolls a 13(15-4=11), he failed to spot John hiding in the debris. John is safe, for now.