The Design Entry HDL (DEHDL or ConceptHDL) .lck files are generated whenever a designer opens a page of a schematic. If another designer attempts to open the same page of the schematic, they will receive a warning that the page is in read-only mode and they will not be able to write to that page. At times, these .lck files become "orphans" and remain after the original designer is not longer running DEHDL. The main cause is if DEHDL crashes.
So, if you determine that nobody is actively editing the page, you may remove the .lck file(s) with no negative consequences.