This feature allows you to merge the records of several clients, sites or equipment and end up with a single up-to-date record.
You can use this feature whenever one of your customers / sites / equipment is obsolete or if you have a duplicate.
It is also useful once your customer database becomes large over time and may require consolidation.

Merging the obsolete or duplicate customer/site/equipment with the target record will combine their basic information, custom fields as well as sites, equipment, jobs, tasks, invoices, quotations, projects, tags, notes and attachments. 

Let's take the example of a customer duplicate :
1 - Click on one of the duplicates (in the client list or in the client's details)
2 - In the list click on the "Merge" button
3 - Select your target Customer
4 - Click on "Preview"
5 - Edit the new client's record if needed
​6 - Click on "Merge"