What function does the「」-shaped component have in characters like「」and「傷」?
Chu bamboo texts show 「偒」, but it's not certain if it has anything direct to do with 「傷」 (they might have represented the same word, but their formation is not the same).

The phonetic component of 「傷」 and 「」 (basically, their right hand side) is reduced from the right hand side of the character 「⿸㫃昜」 (see last three entries here).

「㫃」 depicts a flagpole with an attached flag, and this has now been corrupted into what looks like 「方」 (remnant of the flagpole) and 「」 (remnant of the flag) as a component, in characters like 「旌」, 「旗」, 「旋」, etc. 「」 in 「傷」 and 「」 is from the top right of 「⿸㫃昜」.



References:


裘錫圭《文字學概要》