1. Go prone
2. Crawl forward really close to the stone hedge and keep crawling toward it's end. If it doesn't happen first time try some different angles at the end of the stone hedge.
3. At the end soldier will automaticly stand up and thats really not a good idea when trying to keep your head down in a firefight or when trying to approach stealthy.
4. This "auto stand-up" happens when prone to other objects as well (some rocks etc.) but most notable at the stone hedges.