A lot of what we do involves an extension of uke on a horizontal plane, extending him out over his toes, both in aikido and judo, for that matter. Wonderful, brilliant, great. But there are movements (and they appear in Tegatana no kata, the walking kata) that involve a more "up and down" action.
Not a forceful one, though. And I think it tends to happen after the horizontal extension, at it certainly doesn't involve strength, or trying to push someone down. Here are a few video that got me thinking and exploring it.
I think of it as starting a #2 or #4 release and instead of stepping all the way behind him as we normally do, get to his side (perpendicular) and do the thing in the walk where you lift your hand up and then let it fall down. That's one most folks have no idea where it applies. Well, he's doing it here. He lets uke swing through, raises his arm, and once uke's feet get ahead of his head, the arm GENTLY (like a limp noodle, maybe even lighter than what this guy is doing) comes back down. We played with this in class the other day and it was wonderful.
Then there's the first part of this video:
And these are only two examples of the suddenly limp, noodley arm I've been playing with, and the "downward" collapse (with movement) of everything, especially uke.
Love this stuff.