I'd like to level some posts in the ground (4x4 in cement) to the exact same height. If I use string, there will be some sag due to gravity. For fence posts this is good enough, but for this application I want to get them to exactly the same height, with more precision than I can achieve by using very taught mason's line.

I've never used any kind of optical or laser technology for this. Would something like that give me more precision than a tight string level, without spending real money ? Not being in the trades I'd like to buy something cheap, but not so cheap that it won't do the trick.

I have a big saw to cut thru the posts in one pass using a custom jig to keep the cut exactly square and level, but without exact lines to mark with precise heights across all 8 posts I'm still screwed. For this project we're looking at two rows of 4 posts each spanning 16 feet, which must be perfectly straight, square, and at the exact same height.

Any advice or suggestions greatly appreciated.

I wonder if your local Home Depot has a Bosch laser or similar that you could rent?

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If I use string, there will be some sag due to gravity.

How far apart are the posts?

Use a run of clear plastic tubing filled with water to define the level. Google will provide plenty of examples on how to use this method.

A transit, water Level, laser, or a masons line, they are braided thin and they pull very taught and the sag would be very negligible. We used them all the time.

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Originally posted by BGULL:
Use a run of clear plastic tubing filled with water to define the level. Google will provide plenty of examples on how to use this method.

Neat!

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Originally posted by vthoky:
Bosch laser or similar

I bought one of these when I fenced off my garden (4x4s in concrete). I've found myself using it for a lot of other things since, and have let friends borrow it as well. It was somewhat cheaper back then, but money well spent.

Consumer grade laser levels are affordable and effective. Light doesn't sag (at least over the distances we are likely to use them

You can rent a laser level at many Home Depot’s around the country…

https://www.homedepot.com/p/re...57-LM30PKG/316821764

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Originally posted by BGULL:
Use a run of clear plastic tubing filled with water to define the level. Google will provide plenty of examples on how to use this method.

I was going to suggest building a moat around the perimeter, but plastic tubing would be much easier.

You can rent/buy an engineers level like SMLSIG posted.
Why not run a string?
There’s also 3” levels that will clip on to the string.
2 separate rows? Get 4 smaller levels, clip them on the string right about where you want the post.
2 rows connecting- get 8.

https://www.homedepot.com/p/Em...GEAQYBiABEgLxJPD_BwE

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Originally posted by BGULL:
Use a run of clear plastic tubing filled with water to define the level. Google will provide plenty of examples on how to use this method.

This is what I was going to say as well. Very basic. Very fool proof. Gravity won't let you down.

I made one a few years ago, complete with sticks and yardsticks for measuring water level. I used green auto antifreeze instead of water to reduce bubbles and surface tension in the tubes.

However when I placed them side by side, the water levels didn't always match, because depending on the temperature variations in the water column, I didn't find it accurate enough for perfect precision. But for fencing it was generally good enough unless some of the water column was in the hot sun, and other parts of it was in the shade, so that the fluid density was was not consistent, which would give me false readings. I didn't anticipate that when I built it, but I suspect it would be pretty decent in an environment without environmental differences between different sections of the fluid column. I still have it. I did find it useful however for general rise over run for use in grading dirt and pavers.

quote:

Originally posted by BGULL:
Use a run of clear plastic tubing filled with water to define the level. Google will provide plenty of examples on how to use this method.

Add some food coloring, or like my dad used to do, antifreeze, so you can see the water level more easily

water levels work great set your first post at desired height gravity doesn't lie.

Cheap windshield is what I always used in a water level. The blue is easy to see.

I saw a laser level at Costco today - unfortunately, I didn't note the price and it isn't shown on their website at this time.

Never seen one of those little string levels worth a darn...

Water level. Clear hose the length you need and water

If you use fishing line this will be within the diameter of the line, maybe 50 thousandths or so.

How much closer do you need for something that is in the ground and will be subject to settling and movement?