In the expression "he blockaded me with his chair", what are wheeler's movements being compared with?

By definition, a blockade is "an act or means of sealing off a place to prevent goods or people from entering or leaving."

By checking the context (which comes from "The Celebrated Jumping Frog of Calaveras County") we can have more clarity on this:

"Simon Wheeler backed me into a corner and blockaded me there with his chair and then sat me down and reeled off the monotonous narrative"

The comparison might have been to a wall, or a large object which seals an exit. His movements might also have been compared to a maneuver with tanks or ships that is meant to prevent an enemy from crossing a certain area.

walter refusing lindner's offer.

king hrothgar despair over the inability to defeat grendel