The object of a gatemaze, much like any other maze, is to travel from a start to a finish.
If you want to try out the puzzles you could use one of the following options:
1) Right click on a sample image, save the file and print it. This should work for all samples.
2) Download the gatemaze player application and any sample file (preferably put both in the same folder). Run the application and use File|Open to select the sample file. This should work for square paddocks and under Windows.
3) You could try using a thick marker pen on the monitor but this isn't recommended.