Frequent tipster Kent Cooper is back with yet another solution from a request via the Autodesk forums. MultiLineCloseOpen.lsp includes two commands, MLC and MLO.  MLC stands for MultiLine Close (to close open-ended mlines as if they had been drawn using the Close option at the end), and MLO stands for MultiLine Open (to open closed ones — the converse of MLC). These two commands allow you to open or close any number of mlines in a selection set. As always, Kent’s code is very neat and includes plenty of comments. To get started, load the AutoLISP file and then run either the MLC or MLO command. Select one or more mline objects and then press Enter. Obviously, you can’t open mlines that are already open or close mlines that are already closed. Mlines on locked layers are ignored in either case.