What are the aprons used in Freemasonry?

The fundamental material of a Masonic apron is pure white lambskin, chosen because the lamb and the color white represent innocence and purity of conduct 23. Under the regulations of the United Grand Lodge of England, the apron develops in ornamentation across the three degrees:

An Entered Apprentice receives a plain white lambskin apron, fourteen to sixteen inches wide by twelve to fourteen inches deep, square at the bottom and without ornament or edging 2.

A Fellow Craft wears a plain white lambskin apron of identical dimensions, distinguished by the addition of two sky-blue rosettes at the bottom corners 2.

A Master Mason wears an apron lined and bordered with sky-blue edging up to two inches wide, adorned with silver tassels and three sky-blue rosettes, including one on the fall or flap 2. For Masters and Past Masters, these rosettes are replaced by three emblems composed of perpendicular lines resting on horizontal lines to form right angles 2. Walter Leslie Wilmshurst interprets the Master Mason apron's blue border and rosettes as representing spiritual light, its tassels as the seven-fold spectrum of supernal light, and its emblems as the triple Tau 1.

In American practice, Albert Mackey notes that jurisdictions generally use a plain white lambskin apron for all symbolic degrees, occasionally edged with a narrow blue ribbon 2. Rather than using rosettes or distinct ornamentation, American lodges traditionally distinguish the degrees by the mode in which the candidate wears or folds the apron, such as turning up the flap or corner 2.