You can test for most of these defects by stretching out a bird's wing, releasing the wing, and noticing how the bird folds the wing.
Before you run out and decide none of your Silkies are worth keeping, keep in mind there is no perfect Silkie. Beauty is in the eyes of the judge and the breeder. Breeders and judges rarely agree; judges rarely agree. If we sold every bird with a defect / imprefection we would have no birds at all.
The APA Standard of Perfection (current in 2005) defines Slipped Wing as
"Defects in manner of folding of primary feathers and carriage of the primary section of the wing. Individual feathers may over-lap in reverse order, i.e., over instead of under each other from outer to inner, or there may be a permanent tendency for entire section to be held outside secondaries instead of under; either case or both is a disqualification."
Silkies often have weak wings. The bird does not hold its wing up high and tight to its body.
Over Folded Wing
A Silkie with an over folded wing holds its wing too high.
I can find no references to angel wing in the literature. What follows is just my current opinion. Angel wing is a wing that a bird does not hold close to the body; it sticks out to the side. We have lost to birds with angel wings that their owners readily admitted. Judges often seem to ignore angel wings in Silkies but angel wings are really noticable in hard and tight feathered breeds.
Sometimes primary or secondary wing feathers do not lie flat; they twist or rotate out of the plane of the other feathers. This is twisted wing. Of all these wing attributes, twisted wing is the only one I have seen disappear after a molt.
This attribute is named after Queen Anne's Lace; Queen Anne's Lace was one of the three hens from Jan Bolton that started our line of Silkies. Queen Anne was, as are most Silkie hens, a very special friendly hen. Queen wing is not a defect but just an attribute. Not a single judge commented about this attribute. Queen wing is when one small wing feather in front of the primaries sticks out and points forward. This picture shows Queen wing.