Eilers Wehrstammbuch translations

[flitzen]

I just received my wife's father's military records from the WASt and was delighted to find 40 pages of documents including the Wehrstammbuch and Soldbuch. I translated most of the items on the first page but did not understand the top box outlined in red on the attached scan. The unit looks like something 26 and there is a check mark on the box titled "U" which has no explanation. In the second box highlighted in red does this signify his unit and what would that be. Any help would be appreciated.

[hucks216]

The large H denoted that he was Heer (which you already know). The entry in the box next to this denotes his military speciality, with both the letters and number meaning something. I can't quite read the letters as the image has been cut off across them but it looks like Bau which would be construction although I don't know what extra detail the 26 denotes.
The 'U' box has a cross in it as this signifies that he was an NCO (Unteroffizier).
I don't know what the last outlined box denotes but it might be a serial or registry number.

[flitzen]

Thanks for the info hucks every little bit helps.