This robotic arm is really a lot of fun to build and apply. It applies a 1st and third class lever, and has a exciting linkage for the grabber. It may grab, pick up, and move to the side. A great initial project to warm you up using levers and hydraulics.
You are able to peg the little items that maintain the long arm (as I have), however it requires very exact drilling, so your best bet is to glue the small cross pieces. As soon as the glue is set though, drilling and pegging will make this model last forever ( maybe longer).
Download the simple robotic arm tutorial: