Warp

The warp is the lengthwise grain that runs the length of woven fabric. This is parallel to the edges or selvage

of the fabric and perpendicular to the filler threads or weft threads. The warp threads run in the direction of the lengthwise grain and have little to no stretch. (See also grain and weft)
***

When cutting a pattern it is best to orient the pattern pieces so the lengthwise grain runs up and down the body unless there is a specific reason for not doing so, such as, matching patterns or directional fabrics or taking advantage of bias. This will give the most stability because most garments hang from the shoulders. 

Chasubles, especially, benefit from being layed out on the lengthwise grain, benefitting from the strength of the warp threads.   There is no other support in this free flowing garment.