You found two metal pieces in your garden. One is a magnet, how will you identify that magnet? You are not allowed vyo suspend freely any of the magnet.
Answers
First, the answer of "take one of the bars in your hand, touch the middle of the other rod with the tip of the one in your hand" is definitely the easiest test, and probably the best "correct" answer. If it sticks the same no matter where you touch the tip, then you are holding the magnet. If it sticks less in the center then you are holding the Ni (magnets are stronger at the poles).
Note that this will only work if the bars are rather large. If for instance you have two 1 cm cubes you aren't going to be able to tell the difference in force between "middle" and "end" by just holding them. I think in the case of very small magnets the easiest thing to do would be to slam them together very hard many times. The transition metals (like Ni) are very sturdy while most of the rare-earths that make up most strong permanent magnets are rather brittle. So if you smash them together enough the magnet should start to chip, while the Ni will either stay exactly the same, or maybe a dent/scratch a little. Also, most of these permanent magnets are Ni plated and are a much darker color underneath, so simply chipping off the plating will reveal which is which. Obviously this isn't as nice of a magnetism related solution as the first, but it will likely do the trick just as well (though you will end with a chipped or broken magnet).
the property of magnt is to attract iron things so , the metal pieces attract iron filings it is a magnet