You must have ordered the optional dust shields to go on the Y gantries. One for each side. Peel of the protective covering before installing them. I just finished installing them on mine last night. Very easy to do.
I guess I must have ordered them. Thank you Raillmages!!! I will install them after I true everything up.
@GOAT Since @RailImages has addressed your question, I am closing this thread. Have fun with your new Long Mill.