This does make me thing of another question though. Suppose your opponent plays safe and leaves you a kick shot. It just so happens a piece of chalk is sitting on the rail EXACTLY where you need to kick. It was already there - you didn't put it there. Is it a foul to use the chalk as a reference? Do you need to move the chalk away from the spot to be sure you won't get called for using it as an aid? Obviously it doesn't break the rule of marking the table because you didn't place it there, but what about the other rule (intended use of equipment). Even though you didn't place the chalk in that spot, if you use it as an aiming device wouldn't you be breaking the rule?
WWBD? (What Would Buddy Decide?).......Buddy?

:grin-square:
Intent is EVRYTHING people. No intent, no foul. And remember that, in the event of an argument, intent is determined by the referee! Judge Judy time - simple as that.
The incidental existence of a piece of chalk previously deposited on the rail at the kick point for your shot is totally irrelevant and, if you think about it, it would be totally irrelevant to the shooter. Why, you ask?
Absent of any other assistance, how would the shooter know the chalk was a target if they did not already know the proper aim point???
Sometimes you have to help players (and referees/TD's) logically back into this stuff when players are screaming for a foul with no good reason. It reminds me of an incident that happened a few years ago at BCAPL Nationals:
Player A fouled. Player B, intently studying the lay of the table, walked around to the CB, and then picked up the 1-ball, which was, incidentally, close to the CB. Well, Player B started screaming foul. The ref in the section correctly said no foul, but rather accidental movement under BCAPL 1.33 - replace the 1-ball, pick up the cue ball and carry on.
Player A wasn't gonna have any of it, and demanded a Head Referee. I complied, and listened to Player A argue that it couldn't be accidental movement, because it was impossible to "accidentally" cause your hand to reach out and pick up a ball. (In principle, kind of like the "chalk already on the rail at the aim point" situation.) At that point I asked player A:
"Why would anyone intentionally pick up an OB instead of the CB?"
The look on Player A's face was precious. The 1-ball was replaced, Player B picked up the CB and the world was right.
Side note - The BCAPL is, properly, not a fan of having to back into anything. BCAPL Applied Ruling 1.33 Situation 7 was published because of that incident.
B