Conjuration is the art of creating an energy version of an object. These energy versions have very little physical presence, requiring fine tuning to interact with anything. In combat, it is recommended to keep the shape of this object to the vaguest degree, to save energy and time. With further fine tuning, you can cause these objects to explode on demand. This is a medium/higher tier energy spell due to all the possible applications of such a skill in combat.
Highly skilled magicians can use conjuration to try and crush a person. If they do, it's a contest of will between the conjurer and the victim, if the victim has a higher willpower, then they are unaffected, if the conjurer has a higher willpower, than everything except a person's bare flesh will be affected by the conjuration. I.e, if a knight is caught between two conjuration rectangles, then their armor will bend underneath the will of the mage and try to crush the person inside.