You may feel tempted to lean against a wall while presenting in front of a group, to get a bit of support. However, it will not support the quality of your presentation. You need to make sure that you position yourself on the best spot for presenting, which is not while leaning against a wall.
When you lean against the wall you appear to be cornered, you appear to need support, you appear to want to be part of the wall. Leaning against a wall make you look less confident. Therefore to make a stronger impression you need to have some space around you. In the book that is part of the Public Speaking Kit you will find more tips about the best place to present from.
