Joints in sedimentary rocks are divided into four, the burial, the syntectonic, the uplift and the post-uplift groups. Joints from these groups differ in their various properties. It is demonstrated how sets in specific outcrops can be assigned to one of the four joint groups, and how each group is correlated with specific fractographic features and certain joint charcteristics that play important roles in engineering and environmental projects. In a joint system certain sets may propagate unidimensionally and others may propagate bidimentionally. A wrong appreciation of the joint propagation mode may result in erroneous analyses of joint spacing. Burial and syntectonic joints may develop at much greater depths than uplift and post uplift joints. Joint aperturesmay vary considerably between burial and uplift single-layer joints. Uplift joints may provide better water drainage than syntectonic joints.