Why are jail bars vertical and not horizontal?

Ever wondered why jail bars are always vertical not horizontal? Here are scientific and psychological reasons why the jail bars are designed so.

Imagine steel and what it takes to bend it.  Now imagine standing on a horizontal bar and jumping up and down.  It might bend a little more easily than if you had to pull at it from a vertical position.  It would at least deform more easily.

You’ll notice from others’ answers and images that any time steel bars are used horizontally there are vertical braces placed more closely.  This is because it is easier to use gravity in the favor of one attempting to bend a horizontal bar than to struggle to bend a vertical bar.  ie. escaping from a cell comprised of vertical bars is more difficult than escaping from one comprised of horizontal bars at equal spacing.  So you can effectively use less steel to accomplish a better, more secure configuration with vertical bars.

Plus creating too much of a ladder effect just causes prisoners to behave more sporadically; climbing and clambering above the guards and feigning alpha status from an elevated position.  Psychologically this has a negative impact on the authority of those in charge.

So for security, cost and psychological reasons.