Abstract: Floorboard and openable locking system therefor comprise an undercut groove on one long side and projecting tongue on an opposite long side of the floorboard. The undercut groove has a corresponding upwardly directed inner locking surface at a distance from its tip. Tongue and undercut groove are formed to be brought together and pulled apart by pivoting motion with a center close to the intersection between the surface planes and common joint plane of two adjoining floorboards. The undercut is produced by at least two disk-shaped cutting tools with rotary shafts inclined relative to each other to form first an inner part of the undercut portion of the groove and then a locking surface positioned closer to the opening of the groove. Installation method for a floor of such boards, manufacturing method for manufacturing the undercut groove and a wedge-shaped tool for laying of the floorboards is also disclosed.