Heaving-to

Heaving-to is different for every vessel;  variations on lateral resistance (what's under the water), distribution of sail area, rudder angle, and weight distribution (which affects lateral resistance) ensure that no two boats will heave to in exactly the same way.

Why heave-to?  For some, it's merely a way to cease forward movement of the vessel while a task is completed;  a quick compass bearing and plotting of position, a dash down below for a snack, a minute spent studying a new shoreline with the binoculars.  At other times; a good sleep in heavier weather, a respite from violent motion to cook a meal, or to forestall a nighttime arrival to a new shore.  To retrieve a person overboard, it's extremely valuable to heave-to just to windward of the swimmer to make lifting them out of the water more easy, and (if they are mobile) to facilitate them swimming those last few feet to the boat.

The other day, I decided to heave-to to with the genoa and main.  I wanted to prepare myself and TERN for a riskier move: sailing through a narrow pass with strong currents and the presence of other boat traffic.  First, a quick risk assessment--what could go wrong, what are the probabilities of each "incident" occurring, and what are the consequences of such?

Risks:
1) other boat traffic, and lack of awareness that vessels under sail have right of way
2) sudden loss or change of wind setting me irretrievably towards rocks
3) not enough wind to power TERN through against the current

Probabilities:
for 1) high probability
for 2) high probability
for 3) high probability

Consequences:
for 1) high consequences if a collision occurred. Most potentially costly incident.  Affects more than one vessel/person.
for 2)  possible damage to boat, damaged ego.
for 3)  low consequence, as long as there is room to change course 180 degrees.

Managing Risks:
for 1) visually check for traffic, attempt to navigate channel after traffic has gone through, have VHF radio on and broadcast a "securite" on 16 communicating my intent and that I'm under sail.
for 2) have anchor ready to go (unsecured/all line run free/no tangles), have trusty canoe paddle handy to  use for propulsion, and pivoting.  Also, attempt on a rising tide; kedging off possible if need be.  Have sheets and halyards such that they can run free and be released or tensioned with no snags.  Have outboard ready to use quickly, should the need arise.
for 3) ensure that there is no boat traffic or other hazards behind, so a retreat with the current would be possible.

So, every item on the Management side of things I actually had set up.  There was still a risk that things could go wrong, but by having a management plan, either the probability or consequences (or both) can be reduced.

Heaving-to allowed me the time, with a minimum change in position and a maximum readiness to sail, to grab anything I needed in preparation for the passage through the narrow channel.  This is one of many tactics that engineless sailors use all the time, and for me, it gives a lot of depth and dimension to the activity of sailing small boats.