Stemming from the Oceanic Aboriginal hunting stick (kylie) is the modern sports four-winged boomerang.
In sport there are left- and right-handed styles made from various materials and two types; returning and non-returning. The four-winged sports model shown above is designed to return to the thrower. As soon as it leaves a skilful thrower's hand, the boomerang is destined to journey a certain distance and return to a particular place at a particular time.
To be honest, if I threw one, having never thrown a boomerang in my life, then God only knows where it would land!
This analogy may sound flippant, but after the crucifixion of Jesus on the Cross he rose and ascended to Heaven. The journey had begun which would lead to his return to a particular place at a particular time.
When and where? God only knows.
(See also another throwing cross, the Ninja Star.)