What do you mean when you say seconds ? That site is also confusing for the newbie like myself. It says pack of 10 on 1 item yet the other it just says -10.
Go to Thorne's website front page.
Scroll all the way to the bottom of the page.
Among the text links you will find "download a catalogue".
Download it.
The catalogue has more background info than the web site.
There is a great double page spread with frame dimension details.
Common national frame types are DN4 and SN1. (Not recommended, just very popular - so chosen as examples of the 'code'.)
D is for Deep (standard National brood) takes National Deep foundation
S is for Shallow (standard National super) takes National Shallow foundation
N is for National ... !
Now the type numbers
1 - plain frame (needs some form of spacer), thin (standard) topbar
2 - just like 1 but with a thicker topbar
3 ... uh?
4 - hoffman spaced frame, thin (standard) topbar
5 - just like 4 but with the thicker topbar
So, if you put SN1's in your super then you'll also be needing castellations or those nasty push-on topbar spacers.
I use 14x12 which is a National, but with an extra-deep brood box.
14x12 brood frames are just like DN5's but with longer sidebars. Note that they have the thicker stronger topbar.
In supers I use either SN5's (hoffman + thick topbar) or Manleys (special sidebars & thick topbars).
// ADDED - The Manleys are 10 to a box. I start the SN5's at hoffman spacing, getting 12 into the box. Once drawn, they go onto castellations at a wider spacing, 10 to the box.
Note that all my frames use the same topbar.
The different types are just arrived at by shuffling a surprisingly small number of different parts!
A different pair of sidebars is the only difference between SN1 and DN4 ...
... and sidebars can be bought individually.
Sale "seconds" (sold only in 50's, and being sale-only not in the catalogue) will have the odd knot and blemish. At 50 for the price of about 20 first quality, its a deal many beeks find attractive (even if you scrap one or two from 50). Note that you will need 11 frames for the brood box, and they are sold in 10's or 50's, not 11's ... (so reconsider my comment above about the only difference between SN1 and DN4.)
Its very simple indeed once you get your head around the shorthand.
3 kids bee suites 
with DRSTITSON
). But CW Jones usually sell 50 packs of second quality frames for a little more (about £30.00) their prices for wax foundation are very good as well.
