The SNOMED CT Mapping Tool is used by the IHTSDO Content Team to manage maps between SNOMED CT and other terminologies including ICD-10 and ICD-9CM.
The tool can be accessed here - Mapping Tool
User documentation is available here on the SNOMED International Mapping Tool space.
Source code can be found in the IHTSDO GitHub repository - https://github.com/IHTSDO/OTF-Mapping-Service