8. True, they are high temperature pyrotechnic cutting charges.
These devices were originally developed for Military Explosive Ordnance Disposal Technicians to enable large Bombs to be neutralized by cutting into the outer case of the weapon and causing the contained explosives to burn or detonate as a Low-Order Explosion.
I'm familiar with these devices because I worked in the facility where they were developed, at the Naval Ordnance Station in Indian Head Maryland.
They function by directing the thermal energy from the Thermite into a cutting jet that can cut through inches of Steel in a matter of a fraction of a second. The cut resulting looks much like that made by a cutting torch, except it occurs much faster.
These devices can be manufactured in various shapes and custom designed to produce whatever shape of cut is needed for the application. Since not all beams are of the same size and shape, they can be custom fabricated in advance for every required cut, based on engineering drawings from the original construction of the building.