sides of the mullion 2 the more pressure that is applied the more the spring will tension the reverse would apply to the top spring fig6 is a plan elevation of the base plate 1 illustrating the diagonal receiver slots 8 a for the base plate extension 1 a also shown are the bolt holes 11 used to secure the base plate 1 to the floor the contact points on protrusions 7 are clearly visible fig7 illustrates the base plate extension 1 a in the dropped position where it is engaged with the base plate 1 via the receiver slot 8 now the base plate 1 and the base plate extension 1 a are unified as one part and engage the mullion 2 at 1 b by approximately 3 u2033 making the combination totally secure even if the mullion 2 was to rise above the base plate protrusion 7 the mullion 2 is still held secure by the engagement portion 1 b of the base plate extension 1 a the mullion 2 has now become a non removable mullion the fire rated mullion is simply installed within a double door frame as shown in fig1 the latch housing 3 is secured by fastening means to the door frame header 4 and is centered at the point where the double doors meet the base plate 1 is fastened to the floor and is also centered to where the double doors meet and is aligned flush with the doors the mullion 2 with the base plate extension 1 a which is firmly secured inside the core of the mullion approximately two feet above the floor by using reverse arched springs 10 thereby holding the base plate extension 1 a in place during the handling and cutting the mullion.