As the parts of the knife are all separate objects, the best way to move the object around is by selecting and moving the armature.

The armature is set to display as a bounding box, so is represented by the wire-frame cuboid which will change size and proportions depending on which tools are open and closed. When you open the blend file, the armature will be selected and will appear orange.

To open and close the tools:-

1.     select the armature  
2.     enter pose mode (this is the current view when you first open the blend file)  

3.     select and rotate the relevant blue, arrow shaped bone for the desired tool.

4.     For the tweezers, selecting the longer bone and pressing "G"     will allow you to move the tweezers and selecting the shorter bone and pressing "R" will enable you to open and close them.