It's possible to shorten blinds in 3 quick and easy steps. Fortunately, the job isn’t very dirty and can be accomplished rather quickly. Many retailers provide the service of cutting blinds horizontally, but you’re pretty much on your own vertically.
Step 1: Getting Accurate Measurements
It’s always best to start with an overview in mind. Measure the blinds to see the length needed. Notice when the slats become excess, and mark that for later. Count the slats that are excess, and remove one extra to make sure it fits. Remember, you can do this with any type of blind from faux wood to wood to Venetian. Mini-blinds are generally cheap enough to just replace rather than go through the hassle of shortening them.
Step 2: Remove the Blinds and Adjust
Take the blinds down, and lay them on a chair or the floor. Get your handy screwdriver and unscrew the ends. Obviously, they hold the slats in place so hold onto them. If working with mini-blinds, you will need to remove the plastic plug that holds the string in the casing. You may need to use the screwdriver to pop these out. Pull the knot out, and after you remove the ends, remove the base and the excess slats.
Measure again to make sure your blinds are the right length. Then, reattach the base rail and pull the strings through. Mini-blinds are attached by looping the string around the slats, so remove the loops and then re-loop any that you need to add back into place. Just use the tweezers if you have any trouble. You can cut the string and then tie the little bit at the end into a knot. Stuff that into the holes in the base rail (adjust and trim if they don’t fit). You could also rap the cords around the rail to save them for any future adjustments. It may also be wise to save a few slats if there is a need for adjustments in the future.
Step 3: Re-Hang the Blinds
Replace the plastic plugs for mini-blinds, or attach the rail for Venetian or wood blinds. Hang the blinds, then test the blinds to make sure your base rail is secure. Don’t pull on the adjusting cord to do this, actually lift the blinds by raising the knots. Sometimes blinds end up crooked; in the event of such a situation, just raise the blinds, level them and lower them to the bottom. If this persists, you may need to re-measure and level your trimming.
Once you know the blinds are in place, you can start to enjoy them and use them as you normally would.