Cut out switches are used for many reasons, but are basically a management tool. When in the open position they cut off power downstream. When in the closed position they send power on thru, just like any switch. They should have stainless steel contact points and terminals and a solid insulated handle or throw switch.
You can use cut out switches to turn off unused paddocks and areas not in use. We do however caution you that during periods of heavy vegetation growth that you should probably leave these areas turned on. The energizer can keep the grass load burned down somewhat if it is left on, but if you turn it off and allow grass to get into your wires it may take some time to brown it down again.
We stock several different varieties of cut out switches. They are all priced within a dollar of each other and all work well. Its just personal preference as to which one you like best. We tend to like the ones that you can see from a distance to see if they are open or closed.