When facing the front door, head to the far right to the tool shed. There's a key by the iron. Use it on the lock to the right - it breaks. Now use your screwdriver on the hinges. You get the hammer and nails, plus a gas mask. Use the planks you've found on the hole in the floor and hammer and nail them down. The sign on the wall says to watch out for the floor. Oh great!

Nancy Drew Ghost Dogs Walkthrough