Little black diamond

OK I am stumped...sitting in my workshop, didn't really have a project to do, so I am drinking a beer and bored silly...I started looking at a new tape measure I picked up a Standley 16 ft, got tired of using my other tapes all 25 footers, needed something a little smaller...anyways it had all the standard stuff, markers for feet, red marker for studs, 16 in on center . tested out the break range about 5 foot or so etc... but got to looking and there was these little tiny black diamonds at 19 and 3/16th inch ..every 19 3/16 inch... so I got to looking and all my tapes had it too, except for the really old ones, more the 30 years old ...old...lol...I have no idea what the significant's is for 19 and 3/16 inch, but it must be something recent, because years ago no body cared. Can anyone educate me, been scratching head, why do I need to know that particular distance on my tape measure...

They are for engineered joists or whatever the proper name for them is i believe.

From Stanley: The black diamond marks every 19.2" on our tape rule blades are for spacing Engineered Lumber joists and studs. Several wood product manufacturers offer Engineered Lumber as a substitute for conventional lumber. Span tables for these lumber products provide ratings for spacing of 12in., 16in., 19-3/16in., and 24in. If you multiply these dimensions by 8, 6, 5 and 4, respectively, you'll notice that you come up with 96in., the length of the panels that will be used for sub-flooring or sheathing. Engineered Lumber is usually specified by the architects and engineers who draw the plans. They take advantage of its strength by using fewer joists or studs where codes allow.