-@filter@ groups have a special @properties@ field named @filters@, which must be an array of arrays with 3 elements, each describing a filter. @filter@ groups are virtual groups; they can not own other objects. Filter attributes must include the object type (@collections@, @container_requests@, @groups@, @workflows@), separated with a dot from the field to be filtered on. Filters are applied with an implied *and* between them, but each filter only applies to the object type specified. The results are subject to the usual access controls - they are a subset of all objects the user can see. Here is an example:
+h3(#frozen). Frozen projects
+
+A user with @manage@ permission can set the @frozen_by_uuid@ attribute of a @project@ group to their own user UUID. Once this is done, no further changes can be made to the project or its contents, including subprojects.
+
+The @frozen_by_uuid@ attribute can be cleared by an admin user. It can also be cleared by a user with @manage@ permission, unless the @API.UnfreezeProjectRequiresAdmin@ configuration setting is active.
+
+The optional @API.FreezeProjectRequiresDescription@ and @API.FreezeProjectRequiresProperties@ configuration settings can be used to prevent users from freezing projects that have empty @description@ and/or specified @properties@ entries.
+
+h3. Filter groups
+
+@filter@ groups are virtual groups; they can not own other objects. Filter groups have a special @properties@ field named @filters@, which must be an array of filter conditions. See "list method filters":{{site.baseurl}}/api/methods.html#filters for details on the syntax of valid filters, but keep in mind that the attributes must include the object type (@collections@, @container_requests@, @groups@, @workflows@), separated with a dot from the field to be filtered on.
+
+Filters are applied with an implied *and* between them, but each filter only applies to the object type specified. The results are subject to the usual access controls - they are a subset of all objects the user can see. Here is an example: