The strakes were enclosed by transverse bulkheads of the same thickness. The Viking longship was clinker built, utilising overlapping wooden strakes and curved stemposts. A caret wing is a delta wing with longitudinal conical or triangular slots or strakes. The ships were clinker-built, utilizing overlapping wooden strakes. Ribs were attached to the strakes with cords or trenails, and thwarts installed. Symmetrical ribs or frames were then lashed to the strakes or secured with trenails. Movable flaps at the ends of the strakes effectively made it a three-surface design. The CRJ900 also features strakes located at the rear of the plane. The vortex lift effect is increased by leading edge extensions, known as strakes. The armoured belt consisted of face-hardened Krupp cemented armour (KC), arranged in three strakes. Leading edge root extensions (LERX) are also sometimes referred to as wing strakes. The armored belt was arrayed in two strakes. In very small boats strakes can be made of one continuous piece of wood. They are therefore often described as Scruton strakes. The missile body has narrow strakes extending over most of its length.