For this project you’ll need safety glasses, gloves, a flathead screwdriver, silicone spray, and paper towels. Open sash completely, then remove the sash from the frame by lifting up on the sash and tilting the bottom out of the track. On the bottom of your window there are two assemblies containing plastic wheels. Each assembly has two positions for each wheel, not which position the wheels are in. Then use a flat head screwdriver to remove the wheels by snapping it out of the wheel casing. Raise or lower the wheel to the desired height and snap them back into place. Use previous positions if sliding was smooth. Note that the two middle slots are for the higher position and the two outside slots are for the lower position. Once the wheels are snapped back into place, clean your rollers. Make sure the wheels roll back and forth and there is not dirt or debris in them. Spray your wheels with a small amount of silicone spray. Take a paper towel and wipe down the rollers to ensure there is not excess silicone. To re-install the sash, tilt the top of the sash and insert into the top of the track. Carefully insert the bottom of the sash and push down into the bottom track. Check the sash by sliding it back and forth.