90% of my fishing is quarries and I do well. A depth finder was great, side imaging brought my success to a whole new level.
Structure..........in quarries that can mean old road beds, slight humps, rock piles, corners, depth edges.
One quarry I've fished for years and caught probably my top 30 biggest bass there. First year with side imaging I was cruising through some 30 foot water from one of my spots to another when I spotted a small in diameter but high hump that rose up to 10-12 feet below the surface. The hump was maybe 10 feet across. Fish magnet, especially during the heat of summer.
I another quarry one shoreline is 15-20 feet deep right at the shore for it's entire length. The sun was beating down on it, no shade and I was heading back to the ramp when I noticed a very small indentation in the shoreline, perfect half circle, about 2 feet across so I figured, "why not" and cast a t-rigged craw into it. Nice 4 pounder. There is no other discernible structure that I'm aware of within 50 yards of that spot.