Been collecting information to better define my waters structure for awhile and thought it makes a good topic. This is my edited version from this site-good read: http://www.basspro.com/servlet/catalog.CFPage?mode=article&objectID=30045 Structure terms: Ledge is the beginning of a distinct change in depth. Hump is a shallow area surrounded by deeper water sometimes called underwater islands. Hole is the inverse of a hump - a deep pocket in the bottom surrounded by shallow water. Cut or Trough are elongated holes. Spine is the inverse of a cut, or trough(elongated hole). Some have fingers running off the sides and their gradient, or slope, will also vary from steep to subtle. Like a hump, spines are surrounded by deeper water, with drops and edges on each of their sides. Long spines can be travel routes for fish as they move towards shore, transitioning from deep to shallow water. Breakline is the edge of a drop. Some describe the different breaks as primary and secondary. The primary breakline is the first sharp drop in depth traveling from shore outward; the secondary following thereafter. The last edge being the channel edge. Defining the different structure is just another way of thinking to solve the "Where are the fish today?" puzzle.