IND and BMT lines to create a unified division, the BMT routes were gradually assigned letters for consistency with the IND naming scheme. IRT trains and tunnels are narrower, however, so the two divisions do not mix in revenue service. Diamond services Despite its efforts toward single identifiers for each service, the MTA has adopted a variation of a signage practice that began with street railways, in which a variant service is identified with a special color or symbol on the route number signs. This has been implemented on the subway by use of diamond services. Since a route letter or number is ordinarily presented inside a circle, variants of the same service are shown as the same letter or number inside a diamond shape. In use 6 regular service operates local at all times; weekday peak-direction <6> diamond service runs express in the Bronx (with local service in the same direction cut back to Parkchester). 7 regular service operates local at all times; weekday rush-hour peak-direction <7> diamond service runs express in Queens. F regular service operates at all times; weekday rush-hour peak-direction <F> diamond service runs express in Brooklyn. Former use Until May 2005, rush hour 5 service to Nereid Avenue–238th Street in the Bronx was marked with a diamond with regular "circle" service to Eastchester–Dyre Avenue. Both services were express services in the Bronx between East 180th Street and Third Avenue–149th Street during rush hours in peak direction. Diamond service operated on the BMT Brighton Line while the north side of the Manhattan Bridge was closed for repairs from 2001 to 2004. Full-time local service was designated with a circle Q while weekday-only express service was designated with a diamond <Q>. Other services have also used the diamond before and during the closure from 1986 to 2004; at least one (a brown <R>) dated from a BMT special service using the same number (BMT 2) as the main service that became the R from 1986 to 1988. In addition to the <5>, <6>, and <7>, official maps and schedules used to show several other rush-hour only services with a diamond, including the <4> bypassing 138th Street, <A> to Rockaway Park, <B> and <C> to Bedford Park Boulevard, <D> express on the IND Concourse Line, and the <M> to Bay Parkway. In May 2004, the map was changed to show only the diamond <6> and <7>. The diamond