Mechanical locking system for floor panels

Building panels including a first panel and a second adjacent panel, the building panels comprising a locking system for vertical and horizontal locking of a first edge of the first panel and a second edge of the second adjacent panel, said locking system comprising a tongue and a tongue groove for vertical locking and at least one strip part attached to the first edge of the first panel for horizontal locking, the at least one strip part comprising:

• an upwardly extending locking element configured to cooperate with a downwardly open locking groove formed at the second edge of the second adjacent panel;
• a locking protrusion configured to lock the at least one strip to the first edge of the first panel vertically and in a second horizontal direction against a holding protrusion formed at the first edge of the first panel;
• and
• a fixing element configured to cooperate with a downwardly open fixing groove formed in a rear side of the first panel and to lock the at least one strip part to the first edge of the first panel in a first horizontal direction, said fixing element comprising at least one flexible locking part configured to lock against a wall of the fixing groove.