Weight and grip of sarissa and shield in macedonian phalanx

[Gaius Julius Caesar]

Filling up the body of citizens with the most promising of the perioikoi he created 4,000 hoplites, teaching them to use the sarisa with both hands and to bear shield with strap (ochane), not with porpax.

"The battle being begun, Aemilius came in and found that the foremost of the Macedonians had already fixed the ends of their spears into the shields of his Romans, so that it was impossible to come near them with their swords. When he saw this, and observed that the rest of the Macedonians took the targets that hung on their left shoulders, and brought them round before them, and all at once stooped their pikes against their enemies' shields, and considered the great strength of this wall of shields, and the formidable appearance of a front thus bristling with arms, he was seized with amazement and alarm; nothing he had ever seen before had been equal to it;

"Round before them" to make a "wall of shields" does not fit well with the common pose to me. Then there is the question of what happened when two phalanxes clashed. I assume the shield had some use or they could have just left it on their back until the lines broke up. My guess is that both phalanxes ended up with sarissa "fixed" in their peltae just as the romans did. Maybe the side-on pose with the shield facing the side was used when the extreme 1.5 foot spacing occurred.

Perhaps I am misunderstanding you, but I understood the top passage to refer to the Roman shields (the wall refered to)being pierced and held back from closing with the phalanx, in a frontal formation against formation confrontation.
But I don't see the reference to the Macedonian phalanx forming a "wall of sheilds". :?
Only that they were in formation with rear pikes angled up, so perhaps the 'targets/shields' need to be in position to enable the lowering of the pikes.