There is only one file type that uses the .TCLS extension:
TestComplete Configuration File
Configuration file created by TestComplete, an application that enables users to test applications; contains settings for individual testers of a project or project suite; includes local information such as what paths to tested applications or values of project variables.
TestComplete projects and project suites allow you to test different applications using the same settings. A TCLS file allows you to retain the settings of the project or project suite you are testing locally. A .PJS and .MDS file is similar to a TCLS file but they are used to store broad settings for a project and project suite.
Updated: November 30, 2014