Legal use of hand & arm in blocking?
 

This is the technique I'd like to teach in angle blocking, where the blocker approaches the opponent from an angle from the direction the opponent faces:

It seems to satisfy the requirements of Fed & NCAA, but it looks an awful lot like a tackle. The hand & arm contact only the front of the opponent's frame, but the action at the shoulder will be of adduction to keep the opponent in front of the blocker. It's like carrying something on one shoulder, using the arm to keep it on there.

If that's OK, how about if the hand is placed lower, near the hip, but not quite wrapping around the far side?

Sorry Robert, but I think we're having difficulty understanding what you're saying.

But if it "looks" like a tackle and you take him to the ground, it's probably going to draw a flag.

Visualize the contact as in the table above, and tell me if that's legal or illegal use of hands & arms in blocking.

I'll give you another description: The opponent is facing and moving south, and the blocker is moving northeast. The top of the blocker's right shoulder goes into the opponent's right armpit. The blocker's right elbow is on the opponent's belly. The blocker's right palm is on the opponent's left breast.
The funny thing is that after I posted my question, I watched a video of a team with angle blocking in their "wall" drill, and they were all using that technique on the dummies. However, the dummies were considerably skinnier and certainly rounder than human beings of their size, so the arm attached to the shoulder really wrapped around the dummy, looking very much like a tackle. The funny thing is that they started with that arm in a flipper or chicken wing posture, but still wound up wrapping; backing the dummies was a chain link fence.

I would want the blocker to take the opponent to the ground, though I doubt they'd succeed most of the time, and if that happened, the blocker's arm would wind up across the frame of the opponent on the ground. I just hope the blocker wouldn't land on his chin; he'd probably turn and land on his opposite shoulder. Are you saying that if you saw that, you'd be more likely to flag it?

If this is ambiguous, I blame the rules makers when they dropped the requirement that the hands and arms be kept close to the body (and palms facing the blocker) when blocking with them, because if you take advantage of the current rules allowing hand placement anywhere on the front frame and any amount of elbow extension, it looks like a tackle if an angle block is most effective, even though only one arm is being used. I figure on having the players keep the elbow down and hand up, because if they extend the elbow it's likely to wrap around the waist even if they don't try.

Strangely enough, if they used both hands in an angle block, it would look less like a tackle, because the far hand would push off the armpit and the head would not be behind the opponent while they're in contact, but the block would be less effective AFAICT.

I would say this is a classic holding call. With the blockers head being behind the defensive player, and only the blockers arm being in front of the defensive player. The only thing that is restraining the defensive player is the blockers hand and arm. This is normally called a hold.

Then it would appear the blocker, unless he can achieve a quick knnockdown, has to choose between keeping the opponent from moving south and keeping the opponent from moving west.

Many would advocate in such a situation that I get the blocker's head in front of the opponent, and use the far shoulder to make contact. I'd like to keep my player's head from being in front of a moving opponent wherever possible, and I'm afraid that getting his head sufficiently past danger would leave only the far, trailing arm to restrain the opponent from westward movement, and that arm would have to hook around the opponent's near side to do so. So I think the type of angle block I want to do while being safe and effective would be more likely of the type I described previously, and maybe forego the arm in front of the opponent, turning it into a pure shoulder block, possibly supplemented by a chicken wing/flipper; but that makes for a narrower target.

Here's the video. Actually as I see it now, most of the time the blockers do manage to keep their forearm "inside" rather than wrapping around even the unrealistically thin dummy, although some of the time they do miss and wind up hooking the dummy.

Neither holding nor illegal use of the hands are defined with respect to blocking dummies. :)

Best thing to do would be reach out to a local association and see if they wiould come to a practice or scrimmage. We do that here and it gives a chance to explain what we are seeing and not just throw flags and move on with the game.
We use this time to answer any coaches questions as well. Last year I was working the line at a scrimmage and the interior lineman lined up looking like a "V". I was able to blow the play dead before the snap and have the coach come look at what I was seeing so he could fix the line.