Royal Icing

If you don't want to have to find meringue powder, you can go with my cheating way out! :)

2 egg whites
3c powdered sugar
(can also add 2 tsp lemon juice for flavor)

or

2-3 egg whites (until desired consistency)
1/4 tsp cream of tartar
1lb powdered sugar (approx 3 3/4c)

Have fun!

If you are talking about putting your house together have I ever got the answer for you. Melt a cup of sugar in a pan, electric if you have it. When the sugar is melted it goes a carmel color and you dip the edges of your gingerbread pieces in and put them together. It holds like glue.
Be careful though it burns like a hot glue gun. I use the Royal icing to cover the seams and put on the candy. Another fun thing I do is for windows. After you cut holes in your gingerbread for the windows. Put broken pieces of life savers in the openings put in the oven at 400 degrees, top rack and watch. The lifesavers will melt and you will have windows. If you use butter rum lifesavers you get amber colored windows. I use the 5 flavor lifesavors and they look like stained glass. Good luck on the contest!

Use any recipe with powdered merange. You can buy it at any kitchen specialty store. Definately the best way to go! But DONTput the house walls together with the icing; it takes too long to dry. Instead heat up a couple cups of plain white sugar in a fry pan until it melts and then dip a wall of your house in it and quickly glue it to another wall before it cools. This is very hot and gets a little tricky, but after years of making houses each year I would never go back to waiting for icing to gluet he house again. Trickiest part is drizzling with a spoon on the sections of the roof... But it works out GREAT! Have a blast; it's a wonderful tradition

Buy Wilton's meringue powder. the recipe is inside it and makes the best and hardest royal icing. available at Walmart and specialty stores.