According to Wikipedia, one of the definitions of a Jackknife is as a Pocketknife, and this is defined as follows:
A pocket knife is a folding knife with a blade that fits inside the handle and that is small enough to fit in a pocket. Blades are typically no larger than 3 to 5 in. (8 to 13 cm) in length. Pocket knives are very versatile tools, and may be used for anything from opening an envelope, to cutting twine, to slicing an apple.The one in the picture above is mine and is technically called a Swiss Army Knife. It is made by Victorinox, and the knifes exist in more varieties than you can imagine. I think this one is somewhere in the middle of the range - it has to fit in my pocket, for instance. I am not quite sure what every tool is supposed to be used for, but they are not finicky. They'll withstand just about anything. At least I know the use of some of the more obvious ones.
BTW, this is my third knife from Victorinox. I bought the first one in 1970 and it lasted until the fastening ring finally gave away when we were on vacation in Denmark in 1993. I bought a new one in the nearest city at once.
I would still have had that one if I had not visited Barcelona in 2005. After having checked the luggage at the airport on the way home, I discovered that my knife was still in my pocket. I slipped it quietly into my backpack and hoped for the best. Nothing doing - the courteous people at the Spanish Security persuaded me that I had better leave it behind or stay behind. So Barcelona got one pocketknife richer and I one poorer. It belongs to the story that shortly after take-off, KLM served us food - with a steel knife and a steel fork to go with it.
But there is more: Last October we were on holiday on the island of Crete in Greece. What do you think I discovered in my pocket? Right - my pocketknife - only now I was in the plane, off the ground and on my way home...
As you can see - I still have it.
PS For more about ABC Wednesday, please visit Mrs. Nesbitt's Place. It is well worth the effort.