What do you think this is for?
There's another clue in this photo showing the upper gland tightening nuts removed and not in sight.
|Nuts not tight and out of sight|
|Nuts still not tight and out of sight|
In the vertical engine, the nuts tend to fall in behind the lower gland where your fingers really cannot get. A magnet on the end of a telescopic stick also cannot get there; neither can a magnet dangling on the end of a length of wire (because it sticks to everything else before it gets anywhere near the fallen nuts).
So the top photo has the answer. The copper pipe has a cylindrical magnet clamped in the short end that can be fed in behind the lower gland without sticking to the sides. As a result, it can get to the out-of-reach nuts which inevitably hide in the most awkward corners.
Unless you can stop the nuts falling in behind the glands (some hope), this is the tool for any budding gland worker with a vertical Sentinel engine.