62f31996_L_View_Graphics___Face_Effects__Description
[Effect] arrow [Arguments] tuple! decimal! [Description] 
Generate an arrow image. (Note: to get a better arrow, use the draw effect). An optional tuple! can be used to specify the color of the arrow, otherwise the edge color will be used. The arrow is proportional to the size of the face times an optional decimal value that can be provided. The direction of the arrow can be altered with flip or rotate.
REBOL/View Graphics - Face Effects
Description