Maybe you also remember alleys as long, narrow open spaces where boys tended to hang out - or as the rear accesses to the back lots of houses. Before the days of the attached garage stuck on the front of a house, the carbarn tended to be built on the back of the lot to front on an alley. You can still see them in older areas of this and other cities.

Now veteran writer-editor Grady Clay has produced a 60-page paperback called "Alleys: A Hidden Resource," (Grady Clay and Co., $4.95, Louisville) to remind us that these auxiliary and often-disparage traffic veins can provide signficant contributions in the revitalization of urban areas fortunate enough to have them.

Much of the material is based on alleys in Clay's home base, Louisville.

In the opening chapter of his 60-page paperback, Clay notes that the best-documented alley system in the nation is in the District of Columbia.

"Historically they are a by-product of the famous L'Enfant Plan, which laid out the capital city into large non-rectangular blocks," he wrote. "The city grew, property owners in 1852 cut up the first five big blocks, inserting alleys and selling off back lots; the process spread."

Clay writes about the poor blacks who lived along District alleys. Congress created the Alley Dwelling Authority in 1934 to eliminate hundreds of those substandard dwellings.

But on a visit here a year ago, Clay found "dozens of alley blocks still occupied. But the existing dwellings were in much better shape than in the early 1960s . . . As for older alleys in Georgetown and on Capital Hill, many have become posh homesites for welloff Washingtonians."

Finally, Clay comes up with eight recommendations for better use of existing alleys, including sites for new public structures at minimum cost and disruption.

"None of this need come from City Hall, either on a platter or provoked by a riot," he wrote. "Each of these proposals can begin right in one's own backyard."

Clay is a former real estate editor and urban affairs writer at the Louisville Courier-Journal. He now is editor of Landscape Architecture magazine.