How to Build a "bang in a Box"

This is my first instructable, so I am hoping for comments on what is good and what could be better.

The "bang in a box" is a cardboard box which contain a balloon that pops when the box is opened, it is meant to be used as a practical joke or as a fun and interesting way wrap a gift, its very useful for Party Gift-Exchange games or for other situations where you would like to give the receiver a little surprise



The "bang in a box" was first built by my older brother when he was in second grade, but was pretty big and clumsy and could be set of by bumps or if turned on the side. Since then I have been developing and improving it to the way it works today. The one build in this instructable was build to contain a blanket, and as as a result of that pretty big however i versions i have build previous, it has been a lot smaller thereby making it more suitable for Party Gift-Exchange games. 

All of the materials are easy to get hold of and very cheep or free.

materials:

      * a few cardboard-boxes
      * a few balloons
      * a few clue-gun sticks
      * a pin 
      * gift(optional)

tools:

      * knife
      * clue-gun
      * ruler
      * pencil

first you need to determine what box you want to use, it has to be pretty strong, and has to have the right size, it has to contain the gift, a balloon and have at-least 5cm of room below the gift and balloon for the mechanics. the box must also be opened whit a single lid, how ever this can easily be modified.(see step 3)

Start by closing the lids and gluing them together, next you cut along the top with the knife so you get a new lid. The lid should be completely removable and separate from the box 

cut out of one of the other cardboard-boxes a piece of cardboard that fits inside the box and can be used as a fake floor.

to make the pin holder you cut out two pieces of cardboard the length of the box and glue them together at a 90 degree angel( see picture)
once the glue has hardened, cut out a third piece of cardboard and glue it on at an 90 degree angle, it should be a little shorter than the width of the box.

cut out three ~2 cm width strips(push rods) of cardboard about 15 cm longer than the box is high, clue each end to the bin holder (see picture) 

cut 4 pieces of cardboard about 5 cm wide and 10 cm long, now make a 90 degree bend 2,5 cm from the end in in each end the so you leave 5 cm untouched in the middle(see picture)

now glue the 4 to the floor, leave room for the pin holder (see picture)

* place the gift on the fake floor and draw a line around it.
* cut a piece of cardboard 2 cm higher than the box and 5 cm wider.
* bend it 2 cm in from the bottom and 2,5cm in from the sides so it fits the dimensions of the box.
* glue the bottom fold to the fake floor so it split the box up in a gift- and a balloon part. 
* cut a about 3x3cm hole in the center of the balloon part of the fake floor.
* finally place the pin holder under the fake floor whit the top part of the "T" closes to the hole,
* mark the center of the hole on the pin holder and push the pin through the reinforcing piece of cardboard and out through the top of the of the pin holder and glue it stuck. 

start by placing the pin holder in the bottom of the box and place the fake floor on top of the spacers, when the pin-holder is at the bottom the pin should be about 1 cm below the surface of the fake floor, and when you pull the push rods the tip of the pin should be about 1 cm above the surface of the fake floor. if this is the case glue the fake floor to the spacers and the sides of the box, if not make it so. if you wart to be 100% sure it works you can make a little test (see video)



next make 3 "gliders" they are made by cutting a piece of cardboard about 7 cm wide and the hight of the box and make 4 bends width wise(see pic.) next glue them on to the sides over the push rods.

to finish it of we need to make something that will keep the balloon in place, to do that we make a about 5 cm longer than the balloon part wide times about 10 cm piece of cardboard, bend the ends and glue it to the sides of the balloon part(see pic.) next cut of the push rods and the wall in the middle to a fitting length and carefully glue the spacers to the lid.

rap up the box nicely and try not to scare anybody to death.