Entered Apprentice Masons, the first degree in Masonry, wear their aprons with the bib turned up.
“Brethren, I charge you to regard your apron as one of the most precious and speaking symbols our Order has to give you. Remember that when you first wore it it was a piece of pure white lambskin; an emblem of that purity and innocence which we always associate with the lamb and with the newborn child. Remember that you first wore it with the flap raised, it being thus a five-cornered badge, indicating the five senses, by means of which we enter into relations with the material world around us (our ‘five points of fellowship’ with the material world), but indicating also by the triangular portion above, in conjunction with the quadrangular portion below, that man’s nature is a combination of soul and body; the three-sided emblem at the top added to the four-sided emblem beneath making seven, the perfect number; for, as it is written in an ancient Hebrew Doctrine with which Masonry is closely allied, ‘God blessed and loved the number seven more than all things under His throne,’ by which is meant that man, the seven -fold being, is the most cherished of all the Creator’s works. And hence also it is that the Lodge has seven principal officers, and that a Lodge, to be perfect, requires the presence of seven brethren; though the deeper meaning of this phrase is that the individual man, in virtue of his seven-fold constitution, in himself constitutes the ‘perfect Lodge,’ if he will but know himself and analyze his own nature aright.”
The Meaning of Masonry, W.L. Wilmshhurst, Gramercy Books, N.Y. 1867