I want to test the ability of students to read a passage and answer questions about it. Could you please come up with a good question for the passage "An oscillating cylinder steam engine is a variant of the simple expansion steam engine which does not require valves to direct steam into and out of the cylinder. Instead of valves, the entire cylinder rocks, or oscillates, such that one or more holes in the cylinder line up with holes in a fixed port face or in the pivot mounting (trunnion). These engines are mainly used in toys and models, because of their simplicity, but have also been used in full size working engines, mainly on ships where their compactness is valued.[citation needed]"? 

What feature makes this type of engine valuable for use in small mechanized items?