wall
wall {xpos} {zpos} {upperleft} {lowerleft} {upperright} {lowerright} {depth}{alt}
Creates a 4-sided wall or platform at the specified point.
All of the field except {alt} are the same as they are in holes.
{alt} is used to control the height of the platform. It's measured in pixels. So for a wall with 10 for it's {alt} value would be 10 pixels high, any entity on the platform would be displayed 10 pixels off the ground, and entities would need to jump at least 10 pixels off the ground to get on top of the wall.
If you want to make a wall which can't be jumped on, simply give it a {alt} value somewhere in the lower thousands. Very, very, VERY few entities should be able to jump on it.
In order for enemies to get on platforms higher than their current position, they need a JUMP animation with a range set for it, and/or an animation which lifts them off the ground.
Use
wall {xpos} {zpos} {upperleft} {lowerleft} {upperright} {lowerright} {depth} {alt}
Aside from {alt}, all parameters operate identically to those in the Hole command. All measurements are in pixels.
{xpos} {zpos}
{xpos} and {zpos} are the x and z positions at which the wall is spawned (how far from the start of the stage, and how far from the top of the screen in, respectively).
{upperleft} {lowerleft} {upperright} {lowerright}
{upperleft}, {lowerleft}, {upperright}, and {lowerright} determine the x position of each corner for the wall. Note: These settings are relative to {xpos}, not the stage.
{depth}
{depth} is the z depth of the wall; how far it stretches from {zpos} to the top of the screen.
{alt}
{alt} is the height of the wall. So a wall with 10 for its {alt} value would be ten pixels high. Any entity on the wall would be displayed ten pixels off the ground, and entities would need to jump at least ten pixels off the ground to get on top of the wall.