Every operation needs direction. This is where the letter - also know as the cover sheet, or operational plan - comes in to play. Once a gang structure has been determined, the next step in the stevedoring planning process is writing out how a ship will work. That is, how many moves a crane will do, what type of moves, and at what container bay.
To begin, you must determine a split. The split is how the work that must be done (i.e the number of containers to be moved) will be divided among the cranes you have working. At the base level it is a good rule of thumb to come up with an even distribution of move between cranes. For example, if a vessel had 500 total containers to move and I had 2 cranes to work it, I would ideally want to split the number of moves down the middle so each crane would do 250 moves. If I had 3 cranes to work with, I would want to find a way to have each crane do 166 moves, and so on. However, it is important to keep in mind that this is only a jumping off point for your operational plan.
What cranes do how many moves will be impacted by several factors. Quality of crane operators, out-of-gauge (OOG) moves, ship stores and repairs, crane boom ups, twin 20 moves, etc. Every operation will be different, and must be looked at through its own lens.
Now it is time to write your letter. As you being to plan your operation, it is crucial to give yourself outs. Outs are ways to shift moves from one crane to another on the fly as needed. Normally 'outs' will be bays that are at the extreme ends of the vessel, or segregated from other working bays by bays not being worked by your port. Having outs will help reduce overtime, stress, and possibly save an extra shift if the situation is dire. Throughout your planning process ask yourself "where can I run"? The stevedoring industry is full of surprises, and will often require you to adapt your plan at a moments notice.
The letter is also your directive to the foremen and clerks. Notes showing container size (20, 40, 45, 53), special requests, covering and uncovering of hatches, OOG, and reefers should all be included on the letter so that a foreman knows what to expect throughout the shift, and can give accurate information to his crane operator in a timely manner. Keep in mind that throughout the planning process you are looking at stowage, bookings, and the overarching plan for the operation. Your labor is not, and it is your responsibility to give them the information they need to run a smooth and efficient operation.