MCRP 12-10B.1, page 197

22. Clearing a Room, Entering Through Mousehole. Mouseholes measure about 2 feet wide and are blown or cut through a wall so that Marines can enter a room (Figure A-43). Mouseholes are safer entrances than doors, which can be easily boobytrapped and should be avoided. Procedures discussed in Paragraph 19 are used. The assault element leader positions the covering team to provide security. a. In this situation, Shooter Number One would enter the room through a mousehole after throwing a grenade and waiting for the detonation. b. Shooter Number One will position himself/herself inside the room to the left or right of the mousehole and quickly scan the entire room. He/She then gives the command to Shooter Number Two, “NEXT MAN IN, LEFT (RIGHT).” Shooter Number Two shouts, “COMING IN, LEFT (RIGHT),” enters the room, positions himself/herself against the wall to the left (right) of the entrance, and scans the room. c. The clearing team continues clearing the room as discussed in Paragraph 19. Figure A-43. Entering Through a Mousehole 23. Clearing an L-Shaped Hallway. After entering a room or building, the clearing team may encounter an L-shaped hallway that should be cleared. The following procedures are used: a. The clearing team finds an L-shaped hallway. b. Each shooter takes a dominant position. c. Shooter Number Two aims his/her weapon to cover the dead space (Figure A-44). A - 36 MCWP 3-35.3