בראשית מח:יד פירוש: רש״י, רשב״ם, ספורנו ואור החיים

שכל את ידיו PLACING HIS HANDS DESIGNEDLY — Understand this as the Targum renders it: אחכמינון he put wisdom into them (viz., into his hands), meaning designedly and wisely he moved his hands for this purpose, intelligently and with full knowledge, for he knew that Manasseh was the first-born and yet he did not place his right hand upon him.

שכל את ידיו, as if the Torah had written שכל, both the letters ש and כ with the vowels kametz, resulting in sachal, meaning something distorted, bent out of shape.

שיכל את ידיא, he was quite clear, relying on his sense of touch, without being able to see exactly where his hands came to rest.