I have lath and plaster walls. I want to hang 3 shelves that have hangers
pre molded in the back of the shelves that requires the shelve be placed
over an extended screw head and then pushed downward so that screw head
slides into a slot about a 1/2 inch long and come to rest at the top of the
slot. Hope I described that in great enough detail - if not ask questions!

I went to Lowes to purchase Hollow Wall Drive Anchors and it turned out I
seemed to have more knowledge about what I wanted than any of the employees.
Not enough to actually know what I wanted though. Very, very sad for Lowes
and me too!

Anyway I purchased some anchors made by Cobra. The anchors are not like
other hollow wall anchors I have used in the past in that they do not
require a pre-drilled hole. Supposedly one should hammer the anchors into
the plaster wall. The anchors are equiped with a metal point and a plastic
collar just above the metal tip. Anyway, these things are at least 1/4 inch
thick at their widest so I thought rather than just pounding them in I would
pre drill a hole to reduce the tension when inserting the anchor. Any
thoughts?

My nagging question is, have I purchased the correct anchors? There is a
selection guide on the packaging.

SIZE WALL THICKNESS
1/8" SD 1/8" @ 1/2"
1/8" LD 5/8" @ 7/8"
1/8" SLD 1/8" @ 13/16"

I purchased the 1/8" SLD - which was anchor that was finally recommended by
the store employee. I do not understand what the manufacturer is trying to
demonstrate by the 'wall thickness' in the chart above descriptions. What
means 1/8" @ 13/16" under Wall Thickness?

Thanks for any assistance!