By Matt Slater
BBC Sport at St Andrews
Any golfer caught unawares by the severity of the Road Hole deserves everything they get.
Even "Wild Thing" John Daly is tamed by the Road Hole
The Old Course's 17th is perhaps the most famous hole in the world, and dark tales of the things it has done to people's cards are the stuff of legend.
So there really is no excuse for being surprised at how hard it is - you know about the blind drive, you know about the bunker and what it did to Tommy Nakajima and you know about road at the back of the green, so get on with it.
The 13th, on the other hand, is less famous. There are no highlight reels of what it has done, there are no funny nicknames for its hazards.
But what it does have is a rap sheet as long as a flag stick - this hole has serious previous. It was the second hardest hole in 2000 and it's the second hardest this year.
Called the Hole O' Cross (in), this par-four was one of the five holes stretched by the R&A this year to stiffen the Old Course's defences.
Those extra 35 yards bulked the hole up to a hefty 465 yards and brought back into play the aptly named Coffins, three deep bunkers slap bang in the middle of the fairway between 250 and 290 yards from the tee.
The long and the bold can attempt to fly these traps but it would then require an act of God to stop your ball from running into the rough stuff.
Those confident in their needle-threading ability can drive to a narrow gap to the right of the bunkers, but the safer play is to pull your ball on to the adjoining sixth fairway.
This explains why only 40% of the drives this week have actually hit the 13th fairway.
From here, on paper, things should get simpler as the target you're aiming for is the size of a football pitch. This explains why the greens in regulation figure is so high at 70%.
But finding this green in two does not give you a two-putt sinecure for par. In fact, the average on Saturday was 2.2 putts per player, making it the toughest green on the course.
The 13th shares its short stuff with the fifth, this being the largest of the Old Course's double greens.
With a grassy hollow guarding the left front edge and sand at the right front edge, to get close you must wriggle in between the traps or fly over and pray for a soft landing.
Those coming from the sixth fairway tend to pay for their caution by having to take a longer iron for their second. Not that those coming from the right have it much easier. Any approach inside 20 feet is a small miracle.
And so it proved on Saturday. Of the first 34 players to tackle the 13th only one got anywhere near the hole with his approach.
That was Scottish amateur Lloyd Saltman in the eighth group of the day. His approach got the finishing touch it deserved to record Saturday's first birdie here.
His playing partner Nick Flanagan, however, found the tangled rough in front of the green and chalked up the hole's fifth bogey of the day.
Saltman's effort would not be matched until Darren Clarke marched off to the 14th on the back of a birdie.
The three on their cards was the only similarity between their experiences at 13, as Clarke knocked his approach halfway between the flags for the 13th and 5th only to hole a 60-foot epic for his red number.
Darren Clarke was one of the few players to master the 13th
That birdie was the last the 13th would give up on Saturday. The leaders did well to pass through with their scores unchanged, many did not.
The final reckoning was thus: two birdies, 45 pars, 31 bogeys and two double bogeys.
This was an improvement over the first two days. The third-round average was 4.36 shots, a score that lowered the three-day average to 4.41 shots.
The 13th, in fact, has garnered more bogeys than the Road Hole.
Where the 17th scores more highly is in the absolute shocker column. Nobody has done worse than six at the Hole O'Cross, but the Road Hole has dished out some major pain.
So while the Road Hole's legendary defences can kill you with a single blow, the 13th is more a case of death by a thousand putts.
And its position at the start of the charge for home ensures that it will play a major part in Sunday's final act.