Once a local file has been shared or stored on the server, there is the possibility that either copy will become out of date. This means the file needs to be synchronized, i.e. the local copy and the server copy need to be made identical.
This can happen in two ways. The local file could be modified by the user, or the remote file could be modified. The remote file could be modified if the same user uses CompleteBox on a different machine to upload a change. If this happens, CompleteBox will show that the files are different by displaying a "needs synchronizing" message under the filename, and changing the icon for the file.
A red double arrow means both the local and remote file have changed since the last synchronization. In this case, you will be prompted to select which file should be the authorative one.
A yellow arrow means either the local or the remote file have changed since the last synchronization. When you synchronize, the most recently changed file will be copied over the older file. The arrow indicates the direction of the copy. Pointing to the right means the local file will be copied over the server file, and pointing to the left means the server file will be copied over the local file.
You can also synchronize all out-of-date files via the green synchronize button that appears on the bottom left of the CompleteBox file listing, shown on the left.
Occasionally, you may find that you want to overwrite local changes that you have not yet synchronized to the server. For example, you may have made some local changes, and wish to discard them. This can be done by right-clicking on the filename and choosing More -> Copy file from server. This copies the server file over the local file, erasing the local changes. The Copy file to server menu item does the oppposite, forcing the local file to be copied to the server, overwriting any changes in the server file.