I did a T-nut rail install on my new Daystate Revere!

Chalk string would work, but just like I used to ask my students who layed out on metal with a sharpie point vs a scratch awl- which side of the sharpie is the right dimension? Sharpie, as the chalk line, adds thickness to the line. 

If I did it that way I.D rather use something like 4 lb fishing line instead

Well, if half the thickness of a string is significant, then yes, but that's a pretty anal approach (not a criticism). Heck, I've installed more studs and pic rails from simply eyeballing it, and I have rarely been off enough to notice. And, with the type of bipods commonly used today, like my Acu-tac, it frankly doesn't make a practical difference, as the rifle can be rotated slightly if necessary to square it. And for field use, the average terrain is so far off plum, it matters not at all. I'm not recommending that folks abandon a more precise method, as my eyeballs have gotten pretty good at this over 50 years of shade tree gunsmithing. And, I admit that merely the knowledge of a job well done is worth something. 
 
Ha! You e been lucky! It’s been the opposite for me in my life, lol. The “ eyeballing it” and the “let’s just try and see what happens” stuff has not only caused me to re do things, but also got me in trouble! I find at now 58, I try and take my time and go for methods of precision. That’s why I enjoy some of the posts here on folks that machine, do 3D work, and even when Tominco does his pellet Plac’s for the EBR Contests. These guys are all about precision work. Yes, one can go overboard, that’s why there is that saying about us not building Swiss watches for say, a miter cut on a fence board. It’s good to know we have choices, though!

As far as being anal(I know you meant no disrespect) it was probably from all those years teaching and the students asking me the one question if they chose “an alternate route” than was explained in the lesson, and that same question I got over the years was- “is this good enough”? 

I would ask for them to hand me their project, as if to inspect and critique it. Instead, I would not say a word or look at it, but just toss it in the garbage and say “build it again”. Just like a child not getting their way, oh boy they thru a fit!

Over the years in my trade I’ve seen work start looking shotty, and I’ve learned that it all stemmed from whoever taught the folks doing the shotty work, early on in their careers.
 
Ha! You e been lucky! It’s been the opposite for me in my life, lol. The “ eyeballing it” and the “let’s just try and see what happens” stuff has not only caused me to re do things, but also got me in trouble! I find at now 58, I try and take my time and go for methods of precision. Maybe it was all those years teaching and the students asking me if they chose “an alternate route” than was explained in the lesson, and the same question I got over the years- “is this good enough”? 

I would ask for them to hand me their project, as if to inspect and critique it. Instead, I would not say a word or look at it, but just toss it in the garbage and say “build it again”

No argument, better is better. Having spent about 20 years in BR competition, I get the importance of dealing in thousandths of an inch. I would turn brass to get the necks withing .0005" of concentric. But, having put that behind me, I've learned to really enjoy the pleasure of air rifles and casual target shooting and hunting. If it ain't perfect, but still fun, then it's perfect enough! But, you are obviously a person for whom the pleasure of a job well done is perhaps as important as the measure of its contribution to its use. That's an admirable quality, which I expect a few of your students realized. 
 
Ha! You e been lucky! It’s been the opposite for me in my life, lol. The “ eyeballing it” and the “let’s just try and see what happens” stuff has not only caused me to re do things, but also got me in trouble! I find at now 58, I try and take my time and go for methods of precision. Maybe it was all those years teaching and the students asking me if they chose “an alternate route” than was explained in the lesson, and the same question I got over the years- “is this good enough”? 

I would ask for them to hand me their project, as if to inspect and critique it. Instead, I would not say a word or look at it, but just toss it in the garbage and say “build it again”

No argument, better is better. Having spent about 20 years in BR competition, I get the importance of dealing in thousandths of an inch. I would turn brass to get the necks withing .0005" of concentric. But, having put that behind me, I've learned to really enjoy the pleasure of air rifles and casual target shooting and hunting. If it ain't perfect, but still fun, then it's perfect enough! But, you are obviously a person for whom the pleasure of a job well done is perhaps as important as the measure of its contribution to its use. That's an admirable quality, which I expect a few of your students realized.

Thank you, and you wanna know what happened with that graduating class that I was so hard on? 

Imagine this- it’s about 20 minutes away from the actual handing out of the diplomas. There’s a graduating class of about 300 new journeyman sheet metal workers. It was at the moment where everyone was about finished with their dessert, and one of the students came to my table, which I shared with other instructors(who also taught these same students. The kid asks if he could stand next to me for a photo shoot, while his wife took the picture. I obliged and walked up to the front, just in front of the podium cause we wanted to get the 2018 graduating class banner in the pic.

Once we “had the pose” there was a lot of commotion. Sounds of chairs and tables being pushed aside.

Just like in an epic scene of a movie, I’m gonna guess that 90% of all 300 students got up from their dinner tables, and walked up to surround us all to be in that pic. I was almost crushed with all the arms laying on my shoulders, you know, that “guy hug”.

They all said thank you to me with a handshake as they walked off after the pic was taken. It was the most moving experience in my life. I had to hold back from tearing up.

what I shared here wasn’t meant for me saying I was anything great, not at all. It was meant to let you know that I just cared for their successes, each and everyone of them. That’s all.