When land is surveyed, metal stakes, also known as “irons” or “monuments”, marks the corners of the lot. These markers are typically a hollow, metal pipe, approximately 1/2 inch in diameter and 1.5 feet long. Newer stakes may have plastic caps on top or have the tip painted with a bright color.
The stake may also be buried beneath retaining walls, paved driveways, hedges, etc
上面是自己在网上找到的. 看来是hollow的metal pipe了. 但是从我家survey标的是129, 可从墙跟量到地标是140. 到底按照哪个算啊? 而且我家不是在corner of the lot, 是在两个车库的中间, survey图上专门打箭头标的129的那个位置.