capital
枓 refers to a capital, the top part of a column in architecture. The meaning is specific and technical, with no broader conceptual cluster.
枓 combines 木 (tree/wood) with 斗, which likely contributes the sound. The character is used for a wooden architectural element, but the exact historical development is uncertain.
The left side 木 suggests wood, and the right side 斗 looks like a measuring scoop. Imagine a wooden scoop-shaped capital sitting on top of a column.
For シュ, picture a shoe-shaped wooden capital: shoe -> シュ, and the wooden top of the column looks like a shoe.