Final answer:
The question pertains to the specific types of fittings suited for concealed installations in building systems including water pipes, gas & fire pipelines, and electrical & communications conduit. The focus is on the use of proper fittings like couplings, elbows, and tees, which must comply with safety regulations and building codes. Mention of non-relevant items like hula hoop rings and plastic containers suggests irrelevant material in the question.
Step-by-step explanation:
The question refers to the types of fittings that can be used in concealed locations within structures, such as residential or commercial buildings. Concealed fittings are typically part of systems for water pipes, gas & fire pipelines, and electrical & communications conduit. When installing any of these systems, specific types of fittings are allowed that ensure safety, reliability, and compliance with building codes. These could include but are not limited to couplings, elbows, and tees that are designed to maintain the integrity of the system while being concealed from view. It is essential to use correct fittings that are designed for concealment to avoid safety hazards and to comply with regulations.
Materials like hula hoop rings, five gallon buckets, milk, juice and water bottles, and grocery bags are not related to the installation of building systems and are more connected to consumer products and packaging. Therefore, the mention of these items appears to be a distraction from the main subject of the question.
The knowledge of which kinds of fittings can be used in concealed locations is important for engineering and construction professionals. The materials used in these installations must meet certain standards to ensure the safety and functionality of the building systems.