I've been thinking about this lately wondering how pressure relates to any of the lashings. I didn't think about a vacuum being formed between the two objects. But that would only form a bond along the axis where the two objects where touching.
With the vacuum explanation, it seems to me that a force along any axis besides the axis of the bond would cause the two objects to slide apart. For example, a block lashed to a wall would have a very strong bond perpendicular to the wall since one side would have atmospheric pressure applied and the side with the vacuum would have no pressure applied, but since pressure is equal above and below the block, any push down on the block would cause the block to slide down, I think.
Interesting way to think about pressure though.