Face nail the first few rows of floorboards
The first rows of boards must be secured firmly, here they are face nailed (nailed through the top surface) as there is a Paper DPM under the boards. The first rows must be secured because secret nailing drives a nail at an angle and that forces the boards into the flooring already fitted so it must able to withstand that pressure
Secret nail the floorboards
The bulk of the floor is now fitted by secret nailing (no visible holes/nails in the finished floor). The length of nails must be chosen to give suitable holding power for the floor and not to penetrate the sub floor (avoid pipes and cables).
Face nail final rows of floorbards
Secret nailing becomes impossible when the far wall is reached (see insert) there is no room for the secret nailer, the boards are now face nailed again to finish the flooring installation.