Off the green when chipping or hitting an iron, I like to use intermediate targets within 2 feet of my ball on the target line to assist with alignment, aim, and confidence during the swing. However, sometimes when I look down nothing jumps out at the eye that is perfectly on-line.
Quick research on the rules of golf state that you can't place anything on the ground and leave it there during the swing to help aim. So one time during my previous round, when I didn't see anything helpful on the target line within 2 feet of mall, I just thumped my club on the ground in front of the ball, right along the target line. It barely left a mark and wouldn't be noticeable to anyone but me, as it only slightly smashed the grass down. It served it's purpose, but after doing it I felt guilty and didn't do it again. Is this illegal?