I'm not sure I fully understand what you originally intended to do. Can you try to explain it further so I can better visualize what you are trying to do? That said, how large is the enclosure? What did you use to construct it? What type of floor material is it sitting on? How large is your monitor? How heavy are the logs?
With what information you've given, I can suggest the following:
1) Use a crow bar to lift the corners of your enclosure an inch and insert furniture sliders. Without the friction you may be able to move the enclosure and go about your original plans.
OR,
2) Depending on how heavy the log is, you can attach a lighter/thinner branch from the inside of the enclosure (so that it serves as a shelf) by purchasing hooks designed for coat racks (http://www.lowes.com/pd_89226-89973-P27100-SC_4294856556_4294937087?productId=3061061&pl=1¤tURL=/pl_Hooks+_4294856556_4294937087_) You can secure the end with the holes to the branch via non-biodegradable rope (attach several), drill a series of carefully measure holes in the wall of the enclosure, and carefully guide the hooks into the holes so that the weight of the log forces the end of the hooks against the exterior wall of the enclosure. Think of how peg board and peg board hooks work.
Hope this helped.