I recently asked if anyone knew about using aluminum push-pins for blocking. DON'T!!! :thumbdown: Last night I got my box of push-pins out and tested them along with regular sewing straight pins, and upholstery T-pins. The points of the push-pins rusted overnight and made nice brown spots on the wet cloth I put them in. Apparently only the push part is aluminum. The other pins have no rust on them. It pays to check!!