SharePoint check-out for all: a CDM story

Published 6 November 2025 · by The IAM Cloud team

Cloud Drive Mapper 3.21 brought in a new automated SharePoint check-out feature. Here's what it really means.

The importance of file locking

File locking is important when you're working in a file share. It prevents multiple people creating conflicting versions of the same file, which can be a real pain to untangle.

For decades, desktop developers have worked with Windows APIs and network storage protocols like SMB/NTFS in order to harness file locking for their applications.

SharePoint check-out

SharePoint has its own equivalent to file locking called "check-out" or sometimes "check-in / check-out". It reserves and locks the file for the first user who checks out the file, and ensures any subsequent users who come along only have the option to open the file in read-only. This prevents conflicts.

SharePoint has a few admin options for controlling check-out, including whether you set it as "required" or simply as optional.

Optional is both default and recommended, because "required check-out" has the effect of blocking Office document co-authoring, which is suboptimal obviously, since that can be a really useful collaboration feature.

The problem with optional check-out

Optional check-out, like with the traditional file lock, comes primarily down to the responsibility of the desktop application to manage it. And therein lies a problem. While developers have spent decades handling file locks on Windows and local file shares, very few applications natively support check-out in SharePoint.

Therefore file conflicts are far more common in SharePoint than they really should be. What's perhaps worse is that even if the application does support SharePoint check-out, the implementation Microsoft has provided means throwing the user a pop-up dialog box each time they open and close the file. This has two problems: firstly, it's really quite annoying. Second, the user can dismiss the popup and proceed without checking out.

It's all just a bit sub-par.

The additional CDM-specific problem

With our product Cloud Drive Mapper, we had an additional conceptual problem to deal with. While other desktop application vendors, such as Autodesk, have created SharePoint check-out integration within their software (e.g. AutoCAD), the way they detect that files are hosted on SharePoint is very particular. And what we found is that when working with CDM's drives, AutoCAD could not detect the files were on SharePoint. Meaning CDM inadvertently broke AutoCAD's (and other vendors') SharePoint-aware behaviour.

Check-out for all

CDM 3.21 fixes this. CDM now automates SharePoint check-out on the desktop application's behalf, silently, reliably, and without any popup dialog. The application doesn't need to know it's working against SharePoint. It just gets the file-locking behaviour it expects, the way it always did against a traditional fileshare.

For any desktop tool that touches shared documents, AutoCAD, Office, practice- management software, audit toolkits, document-assembly tools, CDM 3.21 makes SharePoint a much safer place to live than it has historically been.

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