Uncle Al's Simplified One-Page Summary
of the Racing Rules When Boats Meet (World Sailing RRS, Part 2)
(170109)   I lied. Sort of. It's more like two pages: my printer-friendly one-page effort borrowed and updated from my book KISS Your Dinghy is the one page I meant and is intended for racers who already have a rudimentary acquaintance with the Rules. It is a PDF complete with links (that give you the cursor finger, so to speak - click on relevant the number) that will bring up the actual RRS text of the relevant rule or definition as I have it posted in the WIT. On this sheet, I have tried to show how beautifully logically our Rules are laid out. But, as you can of course imagine, this is a very simplified overview and does not cover every eventuality, hence the links to the text of the actual rules and definitions!!

In box 2A, we have the four core rules that regulate racing traffic out on the course. There are three basic possibilities as two boats meet:
a. they are on different tacks, in which case port must keep clear of starboard;
b. they are on the same tack, in which case they are either overlapped or they are not: if they are overlapped, windward must keep clear of leeward; if they are not overlapped, then the overtaking boat (same tack only!) must keep clear;
c. a boat is in the act of tacking, in which case that boat must keep clear of any boat that is not tacking.

Boxes 2B/2C and 2D contain rules that more or less limit the actions of a right-of-way boat when she converges with a give-way boat, by means of the following Rules:
Part 2B:
all boats, whether r-o-w or not, have an overriding duty to do their best to avoid collisions, especially serious ones
15. if a boat acquires the right of way near another boat, e.g. by establishing an overlap to leeward, she must give the newly burdened boat "room to keep clear" but only briefly: the new give-way boat must immediately take (seamanlike) evasive action
For example, on a run, a boat overtaking just to leeward of me from clear astern goes very rapidly from the status of give-way boat (clear astern) to r-o-w boat (leeward), while conversely, I who was clear ahead suddenly become windward boat and have to take immediate avoiding action. Rule 15 ensures that the newly burdened boat is protected to some degree.
16. any course change made by a r-o-w boat near a give-way boat must be done such that the latter - fairly enough - is given "room to keep clear", e.g. a port boat is barely crossing starboard on a beat when the latter gets a sudden lift. Starboard is not permitted to luff up so much that port no longer has "room to keep clear".
17. a boat that becomes r-o-w boat by establishing a leeward overlap near (< two boat lengths) a windward boat is not allowed to sail above her proper course while that overlap continues to exist

Part 2C then deals mostly with restrictions on the right-of-way boat as two or more boats deal with a mark or an obstruction. In essence, their purpose is - again fairly enough - to keep a r-o-w boat from cutting off an inside overlapped give-way boat at a mark or forcing her into an obstruction.
18. the Mark-Room rule is the most complex rule in the book, and deals with what its name suggests - I have given some of its basic details in the PDF (lower left) while adding here links to two definitions that are needed only for rule 18: the zone (which is now three lengths!) and mark-room.
19. an outside overlapped r-o-w boat must give an inside give-way boat room to pass an obstruction such as a starboard r-o-w boat or a point of land, etc.
20. room to tack: if two close-hauled boats are nearing an obstruction (e.g. the shore) near each other on the same tack, and the leeward/ahead boat can't tack without fouling the other boat, leeward is entitled to make windward give her "room to tack" if safety will soon become an issue (e.g. danger of running aground).

Part 2D deals with miscellaneous limitations on all boats on the race course as follows:
21. in a fine book-keeping move, all the exoneration stuff has been put in one easy-to-find spot: rule 21. What it says in essence, that a boat entitled to room or mark-room and that is forced to foul another boat or hit the mark because not enough room was given, shall be exonerated from penalties for breaking rules 10-13, 15, 16 or 31.
22. regardless of other rules of Part 2, the following must keep clear of all other boats racing:
a) a boat returning towards the line after being over early
b) a boat doing penalty turn(s)
c) a boat backing a sail for tactical purposes (as opposed to heaving to which implies safety purposes)
23. obviously - one hopes - we must all keep clear of a boat that is capsized or engaged in rescue activities
24. still under the heading of "it should go without saying": a boat that is no longer/not yet racing must not interfere with a boat that is (note that penalty turns are not available to boats who break this rule because they are not racing at the time of the foul)

My final box goes outside of Part 2 of the RRS to two items that are nonetheless crucial:
31. thou shalt not touch a mark (unless wrongfully forced to do so)
44.2 this rule lays out the turns penalties: what they consist of and when they must be done (a.s.a.p.)
a) one turn for touching a mark
b) two turns for having broken "a rule of Part 2 while racing"