This is a sort of 'one-off' handicapping system for events which require formal and fair stroke play scoring, but where not all the participants may have official handicaps. Company, charity or society days, for example.
Although it appears complicated it is in practice quite easy to use, and through long use has proved itself to be a very fair means of handicapping a diverse group of golfers.
All you need to do is play normally and keep your gross score for each hole. A maximum score of 'twice the par' is applied to every hole, so if you've already taken 8 on a par 4 and are still in the bushes, you can simply pick up and write down 8.
After the round, add up the score and then refer to the chart below. Find your score and look in the right hand 'Handicap Deduction' column. If you shot 96, you can deduct your three worst scoring holes (NB: you cannot deduct scores made on the 17th or 18th holes, even if one or both of them is among your worst scores). So if you have a 7 and two 8s on your card, that's a deduction of 23.
Now look down the chart from 96 to the 'Handicap Adjustment' row, where 96 corresponds to an adjustment of -2. Take 2 from 23 to get 21, and that's your handicap, so you have a net score for the day of 73.