Our sliding glass door was not closing smoothly and was making quiet a bit of noise as it moved. I used a trick I learned from my father-in-law to make the doors glide smoothly again: Paraffin! Now, a quiet whoosh is the only sound the doors make as they glide by! It is easy and frugal to quiet your sliding doors with household wax. You can find paraffin near the cleaning supplies or household goods section of your local grocery store. It can also occasionally be found near the canning supplies.
How to Quiet Sliding Doors with Paraffin:
First, Use a vacuum to remove as much of the dirt as possible.
Then wash out the door guides and dry them. I cleaned half of the guides, then opened the door and washed the other half.
After the guides are dry, run a bar of paraffin over them.
I bought the above box of wax three years ago for a couple of dollars. Although I use it on window jams, zippers, and sleds to make them glide more freely, I still have 3/4 of the box left.