Pop your line out into the rooms through the archway squared up to the walls start there and spline lip tonge and go both ways.
How to get a straight line for hardwood flooring.
Drill pilot holes through the board to prevent the flooring nails from breaking and to avoid splitting the wood.
The first row of flooring should be this distance from the wall on the wider end of the room.
Or pop a line 2 or 3 boards rows out and dry lay to the wall.
Connect both pairs of marks on opposite walls with a chalk line.
Stretch the line to the far end of the course and put it right on the corner of the end of the last piece on the side closest to the wall.
Measure 12 inches in from one end of the wall.
Pry off with a prybar any baseboard or molding from the longest wall in the room that runs perpendicular to the floor joists.
How to find a straight line when installing wood flooring.
Then go to the adjacent wall and snap another chalk line across the room.
Snap a chalk line between these marks or use a laser square to pencil a line.
With it dry laid and tight top nail next to the wall to hold that row then remove the spacer boards to your line and blind nail with your trim gun until your flooring nail will fit without hitting the wall.
Mark this point on the moisture barrier with a pencil then go down to the other end and make a mark a quarter inch away from the wall to allow for an expansion gap.
Drill one pair of holes every six inches down the board and place the holes.
From there measure the width of the plank plus 1 inch into.
The resulting line should run at an angle from your 1 inch mark at one end of the course to the corner of the other end crossing each of the boards that make up the course.
Starting a line for a 2 1 14 hardwood flooring oak floor.