[old_tv_nut]

The side controls are the customer controls. If the set is working properly, they are all that are needed to lock in the picture from rolling up or down (Vertical Hold) and the H is similar for horizontal except that the effect will be that the picture tears into diagonal stripes if it is misadjusted.

Adjusting the controls on the back should only be necessary if the set needs some servicing.

Height does just what you think - shrinks or expands the height of the picture.
Vertical linearity adjusts the picture so top and bottom have the same amount of stretch or shrink. If misadjusted, the picture will look a bit like a fun house mirror.
It is OK to play with these vertical controls to see the effect, as it will be easy to reset them.

I'm not familiar with this set, so don't know why there's a Horizontal Frequency control accessible, but essentially it should set the center point for the H contol on the side. This one could cause you more trouble if you play with it and get lost from the correct setting.
It probably should not be touched unless the side H control cannot make the picture lock horizontally. If that's the case, center the side H control, then adjust Horizontal Frequency for lock. Take careful note of how much you turn it so you can go back if your adjustment doesn't work. It will probably be touchy and have a strong effect, such that good adjustment will occur over only a small range of rotation. Double check that the side H control locks the picture when centered and unlocks it about equally bad when full CW or CCW.