> For the complete documentation index, see [llms.txt](https://docs.dietrichs.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.dietrichs.com/dietrichs-intelligent-documentation/docs-de-en/holzrahmenbau-kompendium/prinzipien-des-hrb-systems/variablen/systemvariablen-offnungen.md).

# System Variables - Openings

In HRB, system variables have been accessible in openings since version 18.01. The following offer particular capabilities:

**ORK** Recess construction. Distance of the window frame from the front face of the wall.

**ONT** Depth of the niche measured from the opening side

**OB** Width of the shell opening as specified in the opening input.

**OH** Height of the shell opening as specified in the opening input.

**OIdnr** Identification number of the window / the door

...

The other system variables are listed in the HRB editor under the Insert → Formula Editor in the group *Opening dimensions* listed.