A depression between two areas of greater elevation, ridges, is usually referred to as a gut or drain. A channel, like a small creek or branch crossing a flat is also referred to sometimes as a gut or drain. In either situation, these objects usually contain the deepest water in the area and fish will use these area as sanctuaries and migration routes. Keep in mind again that deep is relative and that in a shallow water reservoir, a minor change in depth can have major significance. The intersection of two minor drains, or the intersection of a minor drain and a river channel is often holding areas of large concentration of fish and should be sought out and never overlooked.
Notches are depressions, gouges, or ditches into the side of points or humps.
These are the opposite of spur points, but like spur points should never be overlooked as potential hot spots on structure. Notches and spur points could be referred to as structure on structure. Up structure is a collective term for structure that extends upward from the bottom of the lake like points, pond dams, humps or submerged road beds. These structures are normally in the deeper, southern portions of our reservoirs where the depths of the water are normally twenty feet or greater. When the ambient depth is greater than twenty or thirty feet, up structure has much more significance that do creek channels or guts which can be referred to collectively as down structure.