Pipe joint compounds are used to

Pipe joint compounds are materials applied to the threads of pipes and fittings to ensure a tight seal when joining them. The primary purpose of these compounds is to lubricate the threads, which not only assists in easy assembly but also enhances the seal by filling in any small gaps or imperfections between the threaded surfaces. When properly applied, the joint compound can prevent leaks by providing a barrier against fluid passage, thus making connections more reliable and secure.

The other options refer to different processes or materials not directly associated with the primary role of pipe joint compounds. For instance, fusing fittings pertains to welding or bonding methods used in certain types of pipe systems, making gaskets involve creating seals between two flat surfaces, and sealing flanged joints focuses on the use of gaskets or sealing compounds specifically designed for those types of connections. Each of these serves distinct purposes in plumbing or piping systems, but they do not align with the function of pipe joint compounds.