Welded flats
A word or phrase is divided up into pieces (not usually words) that form a base of the given type. Example: the welded second-sound change tech stocks (\teks\ \täks\). The solution need not (and usually doesn’t) have dictionary nature, but the number of “dictionary entries” in the answer shouldn’t be greater than the number of pieces in the base.
The solution: axolotl ballot box (because “axolotlb” transposes to “allotbox”). The solution consists of two dictionary entries even though it contains three words, because “ballot box” is an MW phrase. (Note that the cuewords ROOT BEER BOOT are also a welded transposal.)
Most welded flats divide the solution into two pieces, but occasionally a welded flat with more pieces is seen—either because the given type of flat always has more than two solution words (a word deletion, for example), or because the type of flat sometimes has more than two (a transposal).
The place where the pieces are joined should fall within a word and not between words of the solution phrase (hence the term “welded”).
Welded flats are an Italian puzzle type that Hot introduced to the NPL.