1) Participation 1) Sharing a shack 
A situation when two or more people hold a title to a common property and thereby have a common interest in the property as in joint tenancy, tenancy by the entirety etc.
The situation when more than one person has an interest in real property (such as by signing a rental agreement to share an apartment) at the same time. (See also: tenancy in common, joint tenancy, tenancy by the entirety)