The term “modular” can also be applied to the method of constructing the other components of a template system. For example, a multiwell/manifold template can be described as being modular (even if the well-spacer template was run as a single piece, as the hinged design described above) if the manifold, pigging valve assembly, etc., are installed after the template. The alternative to this type of modularization is installation of a multiwell/manifold template all-in-one-piece/unit. This type of template is often referred to as a unitized template, and a heavy-lift vessel is typically required to install it.
Source: API RP 17A, Design and Operation of Subsea Production Systems—General Requirements and Recommendations, Fourth Edition, Reaffirmed 2011. Global Standards