 Like most of Moore 's work completed after 1954 , this was a modeled sculpture instead of a direct carving . The sculpture is composed of two bronze semicircles , one set inside and at right angles to the other and a slim bronze rod that extends from one end of the outer semicircle to the other that serves as the gnomon ( indicator ) . The bowstring equatorial sundial derives its name from the appearance of the shadow @-@ casting gnomon , which resembles a bow string . The shadow of the rod projects onto the inner semicircle , which serves as the dial face ( or dial plate ) , to mark the time of day when there is sufficient sunlight to produce shadows . 
