Imagery in The Love Song of J. Alfred Prufrock
Eliot uses the ancient Egyptian religious symbol of the scarab beetle, which rolls its excrement into a ball and was said to roll the sun across the sky, to create an intricate image compounded of the vulgar and the divine--a combination which precisely describes Prufrock's view of his situation.
This idea of being pinned to a wall recalls the imagery of crucifixion, in which Christ was nailed (or "pinned") to a cross. It's also reminiscent of butterfly and bug collections, where specimens are "pinned" to display boards. As a whole, this phrase is meant to suggest social anxiety and discomfort, which Prufrock feels whenever he's made to account for himself (his "days and ways").