If you've got a hurricane door or other impact or storm door on your home, you know that simply nailing a wreath or other holiday decoration is not really an option. You could use an over-the-door hook, but if there's little space between your door and the door frame, the hook might not fit. While you could leave your door undecorated for the holidays, there's really no need to if you prefer to decorate. Whether you're dealing with a steel hurricane door or an impact-resistant glass storm door, you can still add holiday decorations without permanently changing the door.
One option is to use a dual magnet set, which contains a metal disc and a magnet strong enough to attract the disc through the door. These need solid door material to work; for example, a glass storm door that has a single pane of glass. The magnets won't work on dual-pane glass because the space between the panes can interfere with the magnets' ability to attract the disc.
If your door is made of metal, you could try using a strong magnet-backed hook. However, whether this works will depend on the strength of the magnet, the thickness of any paint or cosmetic layer, and the type of metal used in the door.
Tape and String Hook
Loop some clear nylon wire or fishing line around one half of an S-hook and tie it securely. Lay the other end of the line across the top of the door and tape the line down with a few layers of strong tape. Look at where the S-hook is touching the door, and cover those parts of the S-hook with moleskin padding (this will protect the door from scratches if the S-hook moves). Hang your wreath or other decoration on the S-hook.
Note that there are two types of S-hooks. One truly looks like an S, but the other looks like an S with one half twisted to be perpendicular to the other half. This type of hook may be easier to lay flat against the door. Both types are inexpensive, so you can get both and see which one works better for you.
Removable Adhesive Hook
You can try using a commercially available removable adhesive hook on the door, too. However, get a spare hook and test the adhesive on a hidden part of the door to ensure the adhesive won't take any paint or other material with it when you eventually remove the hook.
If you'd like to find out the best way to attach decorations to your impact or storm door, contact an impact door company and ask about the specific model you have. There may be products manufactured specifically for that door that will allow you to decorate as normal.