We had a Construction birthday party for my 4 year old son.  First, we sent out invitations that invited all his friends to join "Foreman Jacob's" construction crew at our house which we called the construction site and told them the time to arrive was when their shift started. I made the invitations out of black blank greeting cards from our local arts and crafts store. (They came with paperbag, brown envelopes which were perfect for our look). I took a die-cut front loader and copied it onto yellow cardstock and cut each one out and glued it to the front of the cards. We then printed all the party information on orange card stock and trimmed it with edged craft scissors and glued it to the inside.  The day of the party, we had decorated our driveway with orange cones leading up to the gate to go to our backyard and placed yellow caution tape (purchased at Home Depot)in a large X with a detour sign on our front door  pointing to the backyard.  (This completely fooled our mailman who walked into our backyard thinking he couldn't use the front door to put our mail in the mailslot there). We used extra caution tape around the yard and over plants we to give it a great look. We also took all the construction toys we owned and scattered them across our lawn and on the tables to give it a "real" construction feel. We served chips and snacks in clean, new construction hats and dump truck toys. We used large thermos bottles to serve lemonade and iced tea. We also had a large cooler with other drinks.  When all the children arrived they each received a yellow construction hat (purchased from the dollar store) with each childs name written on the front and back. My 4 year old had "Foreman Jacob" written on it and his little brother was the Assistant Foreman.  I had found small sets of tools at a local grocery store which we hid around the yard for a scavenger hunt.  Each child was given a tool pouch with their name on it and were given clues such as "The Screwdrivers are in the Sand," "The Wrenches are in the water (I put them all in a bucket of water)," "Hammers are under the Hose," and "Combination wrench is behind the Cooler," etc.  I also attached a smaller box to the front of a larger box and painted it yellow, black, and orange to resemble a dump truck. We cut a hole in the top of it, painted a couple of black rings around the hole, and place a bunch of balls that looked like rocks in a bucket next to it so the kids could play "toss the rocks into the dump truck." My son really wanted to play "Pin the Arm on the Crane" so he helped me design a great game and even drew parts of the crane for me.  Each child also received a toolbox that we were lucky enough to find at the dollar store.  I personalized each one before the children arrived and had stickers and foam pieces in toy dump trucks and cranes for the kids to decorate their toolboxes with.  We ended the party with a construction cake with a chocolate cookie crumb road on it which we placed new matchbox sized construction vehicles, road signs, and orange cones on.  We also found construction vehicle candles (Wilton) which added to the theme.  My son had a great time and so did all his friends. I am still having people come up to me to tell us they had a great time. My favorite comment was from one little boy whose birthday was quickly approaching - "Mom, I want to have my party here!"