Marker at the 5-yard link
 

How common is it, in your area, for a marker to be placed on the link that is half-way along the chains?

It is standard in our association. I use neon colored zip ties which make finding the exactly spot fairly quick.

Athletic tape here, from what I've seen.

This is not an association mandate, this is just good common sense. I worked a game Saturday where the school did not have the tape. I tried to get it one of the chain crew to get some tape and put it on the chain, it never happen. We functioned and it was not a big deal. Most of the time the tape is on the chain without having to ever ask.

Peace

My linesman brings his own tape along with two clips and a white beanbag to use inside the 5. We take nothing for granted.

Fairly standard although on older sets that have been "repaired" and the mark is no longer accurate, it can be a bear to cut off the 27 layers of athletic tape used.

I much prefer the new, neon, cable tie method. I even a selection of colors so it will contrast:p

It has been an HL tricks of the trade for as long as I have been working football. Every mentor I've heard talk about the working the chains passes this trick on. it's a quick way for that 5 will get you 1 to be communicated to the Referee on a flag.

While I have never seen it written in any official NFHS mechanics manual there might be some words somewhere on the high school level.

Those words are probably in the CCA manual for NCAA officials. I know they are in the ECAC manual for NCAA officials. We just do it on a regular basis.

For years I carried a small leatheman to remove the huge blobs of tape from chains. I've tried all sorts of "devices", with wrapped tape my least favorite. Use what works for you.

Maybe Honig's can stock a clip with a small piece of cloth that says, "½ way". Just $19.95. :p

Every chain set of the teams I work has one of my (bright yellow) zip ties at its midpoint, easier to see than tape that gets dirty over time. When the crew go round the horn with the down, HL adds the distance so that the white hat will know whether the distance to go will give a 1st if a penalty occurs.
We try to stick to a set vocabulary for distance - inches, short, five, long, ten, two stakes. Very occasionally might use other exact distances, 15, 20 or 25, etc.

I also keep a black or white zip tie with me for repairing the chains if they break. I keep one inside the band of each of my hats, that way I never have to remember to take one out on the field - if I remember to wear a hat, I've got one with me. I've needed it several times so far in my career.