The over head projector projects the image on to a surface you can use it in both daylight and artificial light. You use OHP with special cellophane paper or rolls of acetate. You can create a library of prepared before hand on acetate squares to teach more effectively. You can write with water-based or spirit-based pens on it. You can also sometimes photocopy directly onto acetate squares (Pakkan, 1997).
             One of the benefits of OHP is that the teacher doesn't lose eye-contact with students easily. An OHP is more useful than a blackboard as its surface is horizontal. Besides, an OHP is less messy than chalk.
             Performing a lesson with an OHP has several advantages if you are a teacher. You can hide the parts you want by putting a paper on them. In addition, the teacher can put one empty transparency onto another to build up a complex picture.
             The OHP allows the teacher to perform a lesson successfully. The teacher can take the students attention to a specific point by using the felt-tipped pens. So the teacher needn't turn his/her back to the class. It also eases making exercise by filling blanks the teacher has left while the lesson keeps going on. It is possible for the teacher to cover the answers as s/he is asking questions, and then after collecting the answers, s/he can show the correct ones. It is important that if you use permanent ink pens, you can use your transparencies several times. Furthermore, the acetate sheets can be cut into small strips to provide vivid graphic practice in carrying out word-order changes or the addition, deletion, or substitution of words of or grammatical elements (Pakkan, 1997).
             Teachers and students can stick things on boards-pictures, posters, announcements, charts, etc. this is especially useful if they are metallic boards so that magnets can be used.
             These are small blocks of wood of different lengths. Each length is a different color. The rods are featureless and are on
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