The weight or “bob” is the part of the plumb-bob that is suspended by the string. The weight is symmetrical for balance, and typically has a pointed end for accurate alignment. At the opposite end there is a hole for the string to be fed through and tied.
Most plumb-bobs have a pointed end so as to make it easier to align the tip accurately with a marker on the ground. The finer the point on your plumb-bob, the easier it will be to mark with accuracy.
Some models of plumb-bob come with a cap to protect the tip of the weight when the tool is not in use.
String
The string is a simple piece of thin cord which is attached to a stationary object or construction and from which the plumb-bob weight is suspended. The laws of gravity will ensure that the string is vertical (plumb) and perpendicular to the level (horizontal) ground.
Hole for string
The hole in a plumb-bob for the string to be fed through and tied may just be a simple hole, it may have a ring attachment, or a removable threaded cap which allows the string to protrude directly from the centre of the weight for greater accuracy and balance.
Simple holes
Many plumb-bobs will simply have a hole in the top of the weight through which the string is looped and tied.
Some plumb-bobs have a threaded cap that can be unscrewed from the body and through which you feed the string, knot it and then reattach the cap. This set-up allows the string to protrude directly from the centre of the weight, helping with balance and accuracy.
Ring attachments
Some models of plumb-bob have a ring attachment to which the string is tied.
Reels
Traditional reels
Some plumb-bobs are supplied with a reel so that you can wind the string up when you’re finished with it. A traditional reel is often just a simple spool.
Built-in reels
Some plumb-bobs have a reel built-in to the body of the plumb bob for ease of use.
Box reels
Many modern plumb-bobs have a reel contained inside a box that has extra functions like a magnetic strip and pin to make your job easier.