A lockable flexible element including an attachment and a substantially elongated and flexible body defining a body first end and a substantially opposed body second end, the body defining a body serrated surface substantially longitudinally spaced apart from the body second end. The attachment includes a collar provided substantially adjacent the body second end; a tongue provided at least partially inside the collar and extending substantially longitudinally thereinto, the tongue defining a tongue serrated surface, the tongue being deformable between a tongue extended configuration and a tongue retracted configuration; and a safety catch removably insertable between the tongue and the collar with the tongue between the body serrated surface and the safety catch.