Arrimar el hombro = lend a hand
A nice example of an expression which can't be translated literally. The verb "arrimar" means "to move/bring … closer" in, for example, a sentence like this:
El arrimó el sillón a la pared = He pushed/moved the armchair up against the wall
"hombro" means "shoulder" so the expression "arrimar el hombro" should mean "move a shoulder", but no, it's real translation is "to lend a hand" or just "help".
I've chosen this particular expression because here in Spain we've been forced to hear the expression several times a week for the past six years since the socialist government won the elections. They have an insidious strategy: they decide to introduce a new law or do away with an old one and when the opposition party protests, they say "Estamos intentando salvar/modernizar/cambiar el país y la oposición se niega a arrimar el hombro" meaning "We're trying to save/modernize/change the country and the opposition party refuses to lend a hand". They say this as if the opposition were morally obliged to support anything they propose instead of doing what the opposition is supposed to do: oppose.
Sorry to go off on a small tangent, but the expression becomes quite tiresome when used this way. Hopefully you will find better uses for it.