Apron 

Each and every Pennsylvania Mason wears an Apron during each Lodge Meeting.  The Apron is usually made of white Lambskin and may be embroidered with the Lodge Number.  It may be trimmed in blue.  The Aprons worn by the Officers of a Lodge have the jewel of their office embroidered upon them.  Sometimes the Aprons are made of satin.

As I understand it some Lodges issue each candidate an Apron when they become a Master Mason and they must bring the Apron with them to meetings and take it with them when they visit other Lodges.

Aprons are rather expensive.  Take care of them

Additional Information:

A garment worn over part of the front of the body for protection.  In Freemasonry, the Lambskin or White Leathern Apron is an Emblem of Innocence; the badge of a Freemason.  Every Mason must wear an Apron upon entering a Lodge. (See Ahiman Rezon)

Originally, the Apron was worn as a full skin with the legs of the lamb secured by a tape around the Mason's neck.  It protected the upper part of his clothing when he clasped a heavy stone.  Later as he became more proficient in his trade he had no further use of the upper part of bib, so he let it hang down over the lower part.  The Masonic Apron of today is constructed with a triangular piece overlapping the lower portion.  The significance of the Apron is work.  It is the initial gift of the Lodge to a candidate, and it is the final tribute to a Brother.

From the glossary of "The Exemplar"

The Apron is the first 'gift' that a new Mason is provided with for him to wear.  In our Lodge the first Apron is a plain white Apron.  Wilmington Lodge No. 804 provides Aprons for all our members and visitors to wear at meetings.  All other Lodges that I have visited in Pennsylvania do the same.  I have heard that some Lodges, perhaps the Prince Hall Lodges, expect you to bring your own Apron.

In the Masonic legend of Hiram Abif the Fellowcraft Masons who recanted wore white Aprons as a symbol or Emblem of their Innocence.  We Masons still do.

It is said by many Anti-Masons that Freemasons use the Lambskin, emblematic of Jesus Christ or the Lamb of God, as a way of mocking Jesus Christ or God by using it to cover our genitals, or reproductive organs.  This idea is ridiculous since Freemasonry is not a Religion and does not teach religious dogma or favor any one religion of any other religion.  Freemasons do not care if you believe in Jesus Christ our not, as long as you believe in the Supreme Being. At least the Anti-Masons have an active, distorted and perverted mind.  

When the apron is worn with the flap turned up it becomes a 5 cornered badge indicating the 5 senses or the 5 points of fellowship.  The triangular portion above the rectangular portion indicates that man's nature is a combination of soul and body.  The three angles of the triangular part plus the four angles of the rectangular part add up to seven, or what was considered the perfect number.  It has been said that God loved the number seven more than all things under His throne.  See "The Meaning of Masonry" by Wilmhurst, pages 31-32.