In a Montessori classroom, the guide or teacher, is just one of many teaching aids available to the children and not the most important. We obviously have the many specific Montessori materials which help the child work with their hands in conjunction with their minds and form abstractions of principles. Other materials are the classified cards where children can read and explore for themselves or the 'commands' which provide instructions for the children to follow for geography and science explorations.
One of the biggest aids are the children themselves - teaching one another the concepts they themselves have digested. This also proves to the child that that they have really learnt the concepts. Here is a child explaining to another about the concept of horizontal and vertical.