A floor plank comprising: a top side; a bottom side substantially parallel to the top side, and for affixing to a sub-floor; a first edge extending from the top side to the bottom side comprising: a first contact side extending from the top side to a first terminal position between the top side and the bottom side; and a wedge shaped protrusion comprising; a first horizontal side extending from the first terminal position and substantially parallel to the top side; and a first angled side extending from the bottom side to the first horizontal side; wherein an angle formed between the bottom side and the first angled side is obtuse and an angle formed between the first horizontal side and the first angled side is acute; and a second edge extending from the top side to the bottom side, the second edge having a wedge shaped slot; wherein the first edge of the floor plank is complementary in shape to the second edge of the floor plank so that a second edge of a second floor plank having the same geometry as the floor plank is able to mate with the first edge of the floor plank when the second floor plank is positioned adjacent to the floor plank on the sub-floor; characterised in that: the first angled side includes a cleat located along the first angled side and spaced apart from the bottom side and the first horizontal side; the cleat includes a horizontal cleat side substantially parallel to the first horizontal side; the second edge further comprises a cleft with a horizontal cleft side; and the horizontal cleat side and horizontal cleft side are configured, so that in response to shrinking of the floor plank and the second floor plank in a horizontal direction causing a separation to form between the floor plank and the second floor plank, an overlap between the horizontal cleat side of the floor plank and the horizontal cleft side of the second floor plank is maintained in order to limit vertical movement of the second floor plank. a top side; a bottom side substantially parallel to the top side, and for affixing to a sub-floor; a first edge extending from the top side to the bottom side comprising: a first contact side extending from the top side to a first terminal position between the top side and the bottom side; and a wedge shaped protrusion comprising; a first horizontal side extending from the first terminal position and substantially parallel to the top side; and a first angled side extending from the bottom side to the first horizontal side; wherein an angle formed between the bottom side and the first angled side is obtuse and an angle formed between the first horizontal side and the first angled side is acute; and a first contact side extending from the top side to a first terminal position between the top side and the bottom side; and a wedge shaped protrusion comprising; a first horizontal side extending from the first terminal position and substantially parallel to the top side; and a first angled side extending from the bottom side to the first horizontal side; wherein an angle formed between the bottom side and the first angled side is obtuse and an angle formed between the first horizontal side and the first angled side is acute; and a second edge extending from the top side to the bottom side, the second edge having a wedge shaped slot; wherein the first edge of the floor plank is complementary in shape to the second edge of the floor plank so that a second edge of a second floor plank having the same geometry as the floor plank is able to mate with the first edge of the floor plank when the second floor plank is positioned adjacent to the floor plank on the sub-floor; characterised in that: the first angled side includes a cleat located along the first angled side and spaced apart from the bottom side and the first horizontal side; the cleat includes a horizontal cleat side substantially parallel to the first horizontal side; the second edge further comprises a cleft with a horizontal cleft side; and the horizontal cleat side and horizontal cleft side are configured, so that in response to shrinking of the floor plank and the second floor plank in a horizontal direction causing a separation to form between the floor plank and the second floor plank, an overlap between the horizontal cleat side of the floor plank and the horizontal cleft side of the second floor plank is maintained in order to limit vertical movement of the second floor plank. the first angled side includes a cleat located along the first angled side and spaced apart from the bottom side and the first horizontal side; the cleat includes a horizontal cleat side substantially parallel to the first horizontal side; the second edge further comprises a cleft with a horizontal cleft side; and the horizontal cleat side and horizontal cleft side are configured, so that in response to shrinking of the floor plank and the second floor plank in a horizontal direction causing a separation to form between the floor plank and the second floor plank, an overlap between the horizontal cleat side of the floor plank and the horizontal cleft side of the second floor plank is maintained in order to limit vertical movement of the second floor plank.