|WANT EVERGREEN BORDER PLANT 6
|Your zip code places you in USDA winter hardiness zone 6B although the information in your question indicates zone 5. (I used the following site for reference.)
To some extent your choice will depend on how wide a spot you have in mind and how much sun reaches the site, as well as wind, soil type and so on. However here are a few suggestions. Please keep in mind that 6 to 12 inches is very short for shrubs, evergreen or deciduous.
If width is not a problem and you are just going by height, you could use one of the many cultivars of short (some as low as just a few inches, other to a foot or so tall), spreading junipers. Junipers should do fine throughout zones 5 and 6 and provide a somewhat informal look in a location with full sun and well drained soil.
If you are envisioning a clipped hedge, you could look into some of the smaller boxwoods. (There are some new cultivars reliably hardy to zone 5, and most are fine in zone 6 if planted in a sheltered location with protection from winter wind.) These need a location with at least a half a day of direct sun, wind protection and a well drained soil.
In zone 6 you could also try English ivy grown on a wire frame to serve as a clipping guide. Although this might take more frequent clipping than you would like, it could be grown in sun or shade at virtually any size.
Another possibility toward the taller end of your range would be Euonymus fortunei. It can be clipped and grown as a shrub form, or can be allowed to mound and also sprawl outward. It is semi-evergreen and would be fine in zones 5 and 6 both. It will tolerate sun to shade and needs a well drained soil.
Your local professional nursery staff should be able to help you analyze the growing conditions where you want to plant your border and help you identify plants that would thrive there and also meet your design goals. Based on a more detailed understanding of your planting site and design goals they may have additional or different suggestions. Good luck with your project!