A vertical joint system for substrates is formed with joints and which engaged by relative motion in a direction perpendicular to major surfaces and of the substrate. The joints are configured to enable relative rotation of up to 3 degrees while maintaining engagement of the joints. The joints and are further configured to form two locking planes one on each of the inner and outer most sides of the joint. Engagement about the locking planes is provided by transverse outward extending surfaces. At least one surface in each pair of engaging surfaces is smoothly curved. The joints and can be further arranged to provide a third locking plane parallel to and between the locking planes. The joints are disengaged by combination of a downward rotation of one joint relative the other then application of a downward force.