Hold a straightedge or level against the horizontal window track to determine the location of the bend.
Place a wood block against the bent slider and tap it gently with a rubber mallet to restore it to its original straight position.
Check the level of the repaired section with the straightedge or level. If it still requires straightening, move the block along the particular bent section and keep tapping it until it is straight and even.
Locate the locking mechanism on the horizontal slider and unlock it to allow the slider to move freely. This mechanism is typically located at the ends of the window and includes a tab that you move toward the sides.
Loosen and remove both the screws from the ends of the side rails, using a screwdriver, to allow the sliders to easily move along the horizontal tracks. The screws prevent intruders from opening the window from outside.
Use a pry bar to carefully lift the slider upward, exposing the track’s stoppers. Grasp the stoppers with a screwdriver and loosen these until you pull them free from the track. Have a helper hold the slider in the upward position so you can easily remove the stoppers underneath.
Pull the horizontal slider downward and toward you to release it from its horizontal tracks. The slider slips out easily because you removed the stops. Don’t discard this slider; use it to purchase an identical replacement slider.
Clean the horizontal track with a dry cloth to remove accumulated dirt, grime or debris that may prevent the slider from moving smoothly along it. Even the tiniest dirt particle may hinder smooth movement. Lightly lubricate the track with paraffin or beeswax to assist smooth movement.
Replace the new slider on the horizontal window track. Ensure the slider matches the dimensions of the one you removed. Also place the stoppers you removed back in their original locations. Use a screwdriver to replace both the screws along the sides of the rails.