I don’t know what am I missing here. My algorithm is to select the wall elements, get the name of the “Top Constraint” and work with the name structure and chnge it to a “-5,-4,-3…1,2,3…” structure, when “-” represent the underground levels.
The numbers that come from the string are probably doubles instead of integers. That’s why it can’t find them with IndicesOf.
You need to somehow convert those strings to integers instead of doubles,