Both sheep & alpacas are shorn in the spring and again in the fall, to maintain healthy fleeces.
The sheep are tipped on their bums which helps them to feel secure. The alpacas are also secured to keep the animal and shearer safe from potential kicking.
A farmer can choose to have their animals shorn by eletric trimmers or blade shears.
Originally sheep and other animals were shorn using sharp glass or metal taking tufts of fiber at a time to harvest the fiber but slowly man adapted scissor-like blades to make the job easier. Electric shear machines wasn't invented until the early 1880s.
Some breeds of sheep, otherwise known as "hair sheep" do not require human intervention as their hair naturally falls away on it's own. But who doesn't love the sweet smell of fresh wool?
"But isn't this cruel? It looks scary."
The true reality of it, is that it would be cruel not to shear. Their fleeces would become overgrown and matted if not properly maintained on a seasonal basis.
At the time of shearing, their hooves are also trimmed to a proper length to make walking easier for them. This is also done 2x a year.