。
On Saturdays, I can leave work at noon.
Literal
I [topic-は] Saturday [topic-は] noon [at-に] work [from-から] can-leave.
Two は in the sentence: the outer topicalizes the speaker, the inner topicalizes 'Saturday' as a contrastive time-topic ('as for Saturday, specifically'). 正午 ('noon'). 勤務 ('work, duty, office hours'). ひける is the potential of ひく ('pull, withdraw'), here meaning 'to be able to leave (work).' A slightly unusual construction.