Mock-up panels can be an important tool for communication and quality assurance in masonry construction. A mock-up is more than just the traditional masonry sample panel. In addition to the units and mortar, mock-ups incorporate all of the basic elements of the project's masonry. The construction documents should include enough information to allow bidders to estimate accurately the cost of constructing the mock-up. The Masonry Standards Joint Committee Specification for Masonry Structures requires a minimum "sample" panel size of 4x4 feet. Mock-ups often are larger, particularly when they incorporate more complex design elements. Use only specified products and materials or accepted substitutes to construct the mock-up. Mortar ingredients, including sand and water, also should be those that will be used for project construction because they have a significant effect on mortar color. Because many of the items required in the mock-up may be concealed, the architect or engineer should be present during construction of the panel to observe and photograph the work and answer any questions about specified requirements. To properly evaluate and compare the project masonry with the standards of the mock-up, the architect, engineer, or independent inspector must observe the construction of the building as well.