This always comes up in the practice questions, what is a needle beam and what are they used for?
Basically, these are temporary beams, used to hold up a structure while structural work is being done. These needle beams are often used to hold up a house/building/structure, while doing foundation work. If you have to take out and re do a portion of an existing foundation, your contractor will most likely use a needle beam while the work is going on.
I have found a real life example of a needle beam being used on a construction site in San Francisco. Take a look, and hopefully this will help you understand the whole needle beam concept. Relatively simple, but hard to describe.