Hmm, if you can picture this is your head:
I always drew test tube racks as a rectangle with test tubes dangling down so that it gave the idea of a test tube rack. Labelling and ruling it also helps.
The gauze is just a single horizontal squiggly line sitting on top of a tripod (if it happens to be sitting on top of a tripod).
EDIT: Here's a diagram just in case:
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