I was browsing online recently and came across a website that sells yoga products - books, DVDs, clothing, etc. - and came across yoga blocks. Now, I’ve watched people perform yoga before but I’ve never seen them use blocks. How do they help you?
How do they help me or how do they help one?
Props, in general, allow the practice to fit the student rather than the student having to fit the practice. It should be noted that any prop used over a long period of time is not a prop but a crutch and this is absolutely not the intention of modifying, except for those with very severe physical issues.
Blocks can be used in numerous ways and there simply isn’t enough time nor space to cover them all. Commonly they are used to maintain alignment for stiff students in standing poses (trikonasana, parsvakonasana, ardha chandrasana and the parivrttas of each). However there are numerous uses when the student is creative or the teacher is trained in their use.
gordon
That makes sense. 
If a person were to use yoga blocks in the beginning of their practice, how could they avoid becoming overly dependent on them? Is there a certain time span after which the blocks should no longer be needed?
The practice, by nature, is exploratory. When one stops exploring then the practice becomes rote and loses it’s larger efficacy. Therefore the way most clear is for the person doing the practice to understand and pursue self-exploration.
So “experiment” is certainly one way. Other ways include living the practice such that your awareness is heightened as your practice ages. In this way your self-care is also heightened and you’re more likely to be well rested, well thinking, and well fed. Over time this aids opening the body and obviously a more open body has less of a need for props.
In my class lots of people use them I don’t use them however.it seems some people use the wall for balance when doing some one legged postures also . I was thinking that a balance bar like in a dance studio could be useful perhaps .any ideas on that ?
Cheers
In the spirit of what Gordon wrote above, I think that a balance bar would lead you on to the idea that you need to use the bar, when you might be better off nourishing the idea that you don’t need support. Supposedly the people in your class will not use the wall forever, but aim for a prop-free practice. In the studio I go to all props are cleverly stashed away behind a wall, which keeps the room nicely clutter free and you are not so easily tempted to use props ;-).
I have never practiced Iyengar yoga though. Maybe a balance bar is exactly what you could use for that yoga style, but I wouldn’t know.