Tying a boat to the dock seems to be taken for granted by many boaters and not much thought goes into it the process. Every boater more than likely has seen boats pull into their slip and as the dock lines are made fast to the cleats amidst much hand waving and “discussion” by the skipper about how to properly handle the dock lines.
All dock lines, we have seen, have eyes on each end and the dock lines stay at the dock while we go sailing. The dock lines are then waiting when we return and mooring the boat is as simple as just dropping the eyes over the appropriate cleats and winch. Quick, easy and no confusion by the crew on where the boat goes and the boat is always moored in the proper place.
Cleats should be properly through bolted, never use Lag Bolts to fasten a mooring cleat, Lag Bolts can pull out and the cleat can come loose, flying cleats can cause property damage or even injure people standing by a cleat that comes loose, your boat is now loose in the slip and your boat can be damaged as well as others in the marina. Using two cleats lets the bow of the boat be centered in the slip by the dock lines. We set the length of the lines to have the boat sitting a bit away from the dock so the fenders are not held against the dock.
A few generally accepted guidelines for lengths of dock lines are as follows: Bow and Stern lines about 2/3 the length of the boat, Spring Lines (normal conditions) about the length of the boat and one pair of Spring Lines (for tough conditions) about 125% of the boat length. It is prudent to have more than the minimum dock line count in case your dock conditions are difficult. We carry some extra dock lines of assorted sizes and lengths, two of the spare lines are undersized diameter in case extra shock absorbing is needed. If you are transiting the Ballard Locks in Seattle you also need 2 Lock lines a minimum of 50 feet in length, the diameter sized appropriately for your boat, each with an eye in one end 12 inches in diameter.