Blocking Technique

[Mike Simonds]

Yes, you are correct but remember this:

Assuming National Federation rules: the tackle can make his initial block above the defender's waist and then, as part of the same continuous block (tackle's contact on defender is not lost), the tackle may slide down and perform a crab block against the defender.

This may be done anywhere on the field. The free blocking zone only applies when the initial contact is below the waist.

So to answer your question, any player, at any time during the play, anywhere on the field, may make a legal block and then while in continuous contact with his opponent slide down into a crab block.

Hope this helps.