Uncle Al's Simplified One-Page Summary
of the Racing Rules When Boats Meet (ISAF RRS, Part 2)
My printer-friendly one-page effort 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) that will bring up the actual ISAF 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. However, 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.

Box 2B/2C which is one of two boxes of 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:
14. 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
A boat's tacking to starboard often results in a port boat that was to windward of the tacker, suddenly having to take avoiding action. Rule 15 ensures that this 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 boatlengths) a windward boat is not allowed to sail above her proper course while that overlap continues to exist
You will note that I have quoted some of the more crucial definitions verbatim on the left side of my one-page PDF, including what exactly is meant by keep clear, overlap and proper course.

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 newly named and re-organized 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) plus a quote of 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 closehauled 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 becomes an issue (e.g. danger of running aground).

Part 2D deals with miscellaneous limitations on all boats on the race course as follows:
21. 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 deliberately sailing backwards
22. obviously - one hopes - we must all keep clear of a boat that is capsized or engaged in rescue activities
23. 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"