Set atop bulkhead, pre drilled the two support bars and fasted with 6” lag bolts. My ladder location was along side a piling, so I drilled and added an additional lag bolt for better stability. The installation was very easy and extremely stable.
Due to the slanted angle of the ladder (which is more comfortable than a vertical ladder and easier for children), you actually obtain about 10 inches of vertical drop per step from the mounting surface. Decide length to buy based partly on how high the deck is above the actual water line, and how much distance you will want below the water line so your foot will naturally feel right when coming out of water. Calculate the target number of steps to buy based on distance from deck to first step. Example data -- my 5 foot slanted ladder extends about one foot less deep than my 5 foot straight ladder, so I should have bought 6 foot slanted ladder instead.
The supports just under the handrails sit directly atop of the bulkhead, where the two support bars can be pre drilled and anchored with lag bolts.