If your crossbow comes with a coking device, or your manufacturer suggests that you use one, I would recommend that you heed their warning. These devices assist you in cocking the device. The traditional way would be to place your foot in the stirrup and then pull the entire draw weight yourself until the crossbow was cocked. This method would be quick to tire you out and you would not be able to tell if you were cocking the device evenly. With the use of these aids, you can easily cut your effort in half and ensure that you will get a balanced draw. That can make a big difference in the time that you are able to stay out and hunt as well as in how accurate you will shoot.
Two of the most popular devices are the rope coking device and the crank cocking device. They each offer the shooter the luxury of being able to cock the device with much less effort. Rope cocking devices have two handles on them that are used to pull back the weight of the bow. Somewhere
between the two handles (usually in the middle), you will see two hooks that will be placed on the string to help cock the bow. There are also crank cocking devices that are usually integrated into your crossbow. They cock the device in the same manner that you would reel in a fish. Not every crossbow can use them. Your manufacturers manual will specify if you can use one and which one is best.
Cocking some of these crossbows is no easy task because some of them can reach into the low-200 range for draw weight. The higher draw-weights allow the arrow to be shot at a faster speed, but it limits the person who can shoot it. Whatever crossbow it is that you are shooting, I will always recommend that you get some sort of cocking device. Why would you want to work harder to pull back the string when there is a perfectly good option that is already out there?