The Shadow Imitation Technique allows the user to extend their shadow for as far as it has sufficient area. Once it comes into contact with a target's shadow, the two merge and the target is forced to imitate the user's movements. Therefore, the two can throw shuriken at each other at the same time if the user desires that. (Of course, to prevent hurting themselves, the user just has to have the shuriken holster in a place where you don't normally have it, like the back.) If the target is out of range, the user can produce a better light source to increase their shadow's size or rely on preexisting shadows for their shadow to freely travel through.
The major downside of the Shadow Imitation is that it is tiring to use repeatedly; Hidan notes that the ability is subject to some form of diminishing return and decreases in potency after repeated use. If the user is low on chakra, the performance rate of the technique also deteriorates. Insufficient lighting will make the jutsu less effective. A particularly strong opponent can also resist the shadow's forced imitation.
Shikaku Nara calls this jutsu by its old name: the Shadow Bind Technique (影縛りの術, Kage Shibari no Jutsu; English TV "Shadow Paralysis Jutsu"). The old version simply paralyzed the target. The imitation aspect was apparently added sometime between Orochimaru's defection from Konoha and his later invasion of the village.