Help needed with understanding accuracy in measuring tools. I want to go straight :-)

[Boyan Silyavski]

PS.
Just discovered on the page of the DIN 874 straight edges, that there is another page. Its called: Straight Edges made from Steel, no DIN, Testing Accuracy in Item Description, Faces grounded, Length from 500 mm to 6000 mm. Here are the even cheaper " scrap like" :-) edges. Scrap for them, treasure to me.
Example:

enght 2000 mm, height 40 mm, width 8 mm


Straight Edges Steel
finely ground,
Tolerance flatness: 112 µm,
Net- weigth: 4,8 kg

Made in Germany

Price without Tax: 114,50 EUR
Price incl. Tax: 136,26 EUR

So 112 micrometers =0.112 millimeters, and thats for 2 meters. Not bad for 136 euro. If i make a big build i will definitely buy one similar

[Greeny]

This one looks ok.
MeasureShop.biz: Flat straightedge, steel

Part no: 1689 104
2000 x 60 x 12mm
din 874/2. 58 micro meters
£111.80 + vat