This is a bracket providing support for opengrid mounted horizontally when using wall-mounted opengrid. The bracket itself is parametrically defined inside of FreeCAD. It should be compatible with all openGrid types sized normally (normal/lite/heavy). I have not tested adjusting the metrics for non-standard grid sizing.

The model parameters include the total bracket size and offset. Total bracket size is the number of openGrid cells the outer arms are sized for. Offset controls the number of cells the corner is sized out from. There is a minimum offset size of 3 and the total size must be 2 greater than the offset.

I have found the chamfering to be fairly stable, but if you need to reapply chamfering, every edge aside from the edges at the faces of the four arms should be chamfered. If you'd like to use a different mounting system, the sketch has vertices centered on the arms you can use to attach your mounting part.

The provided 3mf example is 7 total, 3 offset sized. I can provide additional sizes on request, but I will not be providing additional mounting options as getting the attachment placed exactly is somewhat time consuming.

I have a sample shelf model to use for this support on my profile, but you can just use any openGrid boards of the desired size for your own purposes.