Some translations set each line of poetry farther to the right than the rest of the text to make it easier to read. The ULB does this with the poetry in 13:15-27.
The action of hiding the undergarment was intended to be a symbolic event. It was supposed to get the Jews' attention and be a lesson for them to learn. Jeremiah performed the action, but it was not the action itself that was important. (See: [[rc://en/ta/man/translate/figs-explicit]])