Labor Day weekend is an appropriate time to pay homage to the labor that produces both beautiful architecture and sound construction.

We talk routinely about the "labor and materials" required to build. But when a building is completed, we see and remember primarily its geometry -- of form and space -- and the visible materials used to render that geometry. The time and skills needed to craft all the seen and unseen elements of a building are easily overlooked.

We also often forget that quality of labor, as well as quantity, contribute substantially to architectural success.

In the aggregate, the building construction industry is among the nation's largest employment sectors. Millions of skilled, semiskilled and unskilled laborers are involved in obtaining and processing raw materials, fabricating countless products, transporting and distributing those products, and assembling them in buildings at thousands of active construction sites every day.

And don't forget all the people, skills and talent involved in designing buildings and construction products and the professional labor invested by hundreds of thousands of architects, landscape architects, engineers, interior designers, industrial designers and specialized technical consultants.

As an architect, I appreciate how construction workers can often accomplish the seemingly impossible, beginning with the ability to read and interpret complex, potentially confusing and occasionally conflicting design drawings and specifications prepared by design professionals.

I am always impressed when something that begins as a drawing, whether on paper or digital, is executed successfully in three dimensions. This is especially true of construction demanding critical labor coordination, painstaking craftsmanship, fastidious handling, and precise installation and finishing.

We designers can labor over and conceive ingenious forms and details, delineating them perfectly in design documents, but proper implementation in the real world can be daunting -- and sometimes impossible. Most builders can recount at least one anecdote about some architect's design detail that defied execution.

Fortunately, construction contractors, subcontractors and their employees can usually figure out how to achieve challenging design intentions, both technically and financially. And many also succeed aesthetically, producing degrees of exactness and finish that meet or exceed expectations.

Not all types of construction enjoy or need the same quality of labor. Some labor skills appropriate for institutional, civic, educational and custom residential buildings are notably higher than those required for production housing, strip shopping centers or warehouses.

Carpenters who erect the structural framing for garden apartments and subdivision homes are not the same carpenters you would hire to build cabinetry and millwork in a courtroom or high-end kitchen.

Construction labor continues to become more specialized. For example, companies that furnish and install sophisticated curtain walls of glass, metal, dimensioned stone or precast concrete depend on highly trained employees with considerable expertise in curtain wall technology. They must understand not only how such walls are assembled but also how to account for moisture infiltration and thermally or seismically induced movement.

Today's licensed mechanics, plumbers and electricians likewise require ever more training, experience and expertise to deal properly with increasingly complex technical systems, equipment, engineering standards and ever more arcane building codes.

General contractors now depend totally on specialized subcontractors and labor for almost every aspect of building construction: demolition, debris removal, grading and excavation, site utilities, foundations, scaffolding, construction cranes, concrete work, structural steel framing, masonry, insulation, waterproofing and roofing.

Thus, when a building is finished -- paint dry, windows cleaned, carpets installed, railings and doorknobs polished, equipment and appliances operating, landscaping in place -- and you admire it, recall the thousands of hours of labor that went into its creation.

Recall how much you don't see. And briefly ignore the few defects -- leaks, misalignments, drywall cracks -- that inevitably occur.

Finally, remember on this Labor Day that, although architects get most of the public attention for their design ideas, attention should be paid to those whose labor transforms design ideas into real buildings.

Roger K. Lewis is a practicing architect and a professor of architecture at the University of Maryland.