Floor covering comprising a plurality of unit panels (1) laid in a pattern, these panels being provided on their head sides (2, 3) and on their longitudinal sides (4, 5) with locking strips (6, 7) which engage with one another in the assembled position in which unit panels (1) are arranged adjacently within a covering, wherein grooves (19, 20) are provided in the head sides (2, 3) and wherein the grooves (19, 20) of two abutting head sides (2, 3) correspond and form a locking channel (21) intended to accommodate a head tongue (22, 22a-k). The head tongue (22) is preassembled in the groove (20) and projects beyond an end of the groove (20) that faces the longitudinal side (5) of the unit panel (1). At the same time, the head tongue (22) in the preassembled state is embedded completely within the groove (20) and can be displaced at least partially from one groove (20) into the corresponding groove (19) of the adjacent unit panel (1) by sliding the projecting end (24) of the head tongue (22) into the groove (20).