I’m not sure if this is common only in the Theravada tradition, but why do the monks often have the right should bare?
Anybody? 
It’s their pitching arm?
The right arm bare has no particular significance in itself that I know of; it’s more a matter of the logistics of wearing a simple robe.
Buddhist robes in their original time sense were garments sewn from cast off material, often rags, and before complex sewing machinery. The simplicity is to symbolize renunciation. The basic robe model is a piece of cloth worn around the waist, and another wrapped around the upper body.
From this site:
"There are a number of ways the monks wear their robes (depending usually on their sect and country). The most universal one is that which is worn for the alms-round when the robe is covering both the shoulders. The two top corners are held together and the edges rolled tightly together. The roll is then pushed over the left shoulder, down the back, under the armpit and is pressed down with the left arm. The roll is parted in front through which protrudes the right arm.
Within the monastery or residence and when having an audience with a more senior monk, a simpler style is adopted (as a gesture of respect and to facilitate work). The right side of the robe is pushed under the armpit and over the robe on the left leaving the right shoulder bare."
In warmer climates like Thailand, a Therevada Buddhist country, that works well. As Buddhism spread throughout Asia, adaptations were made in robes for climate and social conditions. But, basically, dress for a Buddhist monk is to be as simple and functional as possible, uniform in identifying one who has renounced the outward world. Female Buddhist renunciates tend to have more discreet dress.
Does make me wonder about left-handed monks, and if they wrap their robes opposite to facilitate their best pitching arm.
I say it’s the Flashdance look. In the more isolated areas of Southeast Asia, it’s never really gone out of fashion.
At risk of going to a Buddhist hell, and with apologies to Michael Sembello…
“Mahayan”
Just a still town boy on a Saturday night, lookin’ for the path of his life
In the real-time world no one sees him at all, they all say he’s crazy
Locking rhythms to the beat of his heart, chanting mantras into life
He has tranced into the danger zone, when a trancer becomes a trance
It can cut you like a knife, if the gift becomes the fire
On a wire between will and what will be
He’s a Mahayan, Mahayan on the floor
And he’s chanting like he’s never prayed before
He’s a Mahayan, Mahayan on the floor
And he’s trancing like he’s never tranced before
On the rice-fed dojon sanity is a place most never see
It’s a hard warm place of a monast’ry, touch it, but can’t hold it
You work all your life for that moment in time, it could come or pass you by
It’s a push of the world, but there’s always a chance
If the hunger stays the night
There’s a cold connective heat, struggling, stretching for defeat
Never stopping with his head against the wind
He’s a Mahayan, Mahayan I sure know
And he’s chanting like he’s never prayed before
He’s a Mahayan, Mahayan I sure know
And he’s trancing like he’s never tranced before
(Solo)
It can cut you like a knife, if the gift becomes the fire
On a wire between will and what will be
He’s a Mahayan, Mahayan I sure know
And he’s trancing like he’s never tranced before
(repeats out)
(What is the sound of one hand clapping, reluctantly?) 
He should apologize to the rest of us!
That was some funny stuff - thanks!
I love that Elelle posted her answer from nirvana.
Scrivener, that was wonderful…no Hell for You, laughing joy man!