Note: This device is intended for use during an active intruder emergency only, it is not placed on the door at any other time. It is NOT intended for use as a normal door lock. The idea is to do anything we can to slow down an intruder from getting into the classroom It be attached in less than 15 seconds by students or teachers. It cost less than $15.00 to make and is rather simple in design and construction . It only works on door that swing outwards, a second piece is in the works for doors that swing inward. This design is offered for anyone to copy and adapt for their use.