Concrete Finlock gutters were briefly popular in the 1960s and 1970s and comprise of small sections of concrete that locked together and cap off the top of cavity walls forming the wall plate and as such supports the roof structure/rafter ends etc. The majority of these installations have been found to leak on the joints which not only discharge down the outside of the walls but also into the cavity causing internal dampness which can often bedetected at the junction of the ceilings and walls and particularly at the head of windows. This has also been known to cause wall tie corrosion. There are many solutions to overcoming the problems of leaking Finlock gutters including cutting the outer concrete surfaces off, fitting fascia boards and a traditional gulley gutter. Other solutions are to extend the roof coverings over the top of the gutters and again fix gutters using steel fixings secured into the concrete. More commonly however, these are lined most commonly with glass reinforced plastic but there are also self-adhesive zinc liners widely available. There have been attempts to coat the inside of the gutter with bitumen but this is rarely effective.