Getting benefit from something, unintentionally. Abaye's example is a story of R. Yochanan ben Zakkai enjoying shade from the wall of the Beit HaMikdash, as he taught. Other examples from cleaning the Beit HaMikdash - how they actually did their work. Also: sights and sounds and smells - and the benefits or enjoyment that they bring - are more abstract, and less tangible... with smell being more definite. How and to what extent is this applied? Note that the halakhah expects people to get enjoyment or benefit from their senses. Plus: A garment merchant who wears his wares, including shaatnez garments. And plus: Not using chametz to fuel a fire, even as it's being destroyed. Or orlah. Etc. A harsh psak - taking the issues seriously.