What does BLST stand for?

Ballast

Mixed size aggregate. OR Framed walls (generally over 10' tall) that run the entire vertical length from the floor sill plate to the roof. This is done to eliminate the need for a gable end truss. OR A transformer that steps up the voltage in a florescent lamp. OR A device that by means of inductance, capacitance, or resistance, singly or in combination, limits the lamp current of a fluorescent or high intensity discharge lamp.