# Strategies better than brute force for solid-color areas of a jigsaw puzzle, where the pieces have the same general shape?

I have a jigsaw puzzle that I've been working on for a while where I have somewhat stalled out because the remaining pieces/areas are all solid black (or if there are color variations between them, they're too subtle for me to make out). I would estimate based on the puzzle's listed total piece count and the remaining area that I have between 100 and 300 pieces left.

In searching for tips on how to finish this puzzle off efficiently (including here), the main advice I see for this situation is to sort the remaining pieces by the arrangement of holes and pegs that they have. The trouble is that this puzzle's pieces (excepting the edge pieces, of course, but the border is finished already) all have the same arrangement: two pegs across from each other and two holes across from each other. I haven't found / haven't come up with any great search terms to find tips that are specific to this scenario.

I've tried to sort the pieces by other traits that I can pick out--whether a piece seems "wider" than most of the other pieces, or whether the flanges(?) on one side seem particularly thin--but the resulting classification seems subjective, pieces can overlap those categories, and it seems fairly rare (unless a remaining hole in the puzzle is surrounded on all four sides) that I can tell for sure whether a particular spot in the puzzle will require a thin-flange or wide piece, so the classification doesn't seem to be gaining me much.

The last progress I made was done by brute force, picking a spot and trying every piece one at a time (in two orientations). This seemed to go faster than when I was trying to brute force by picking a piece and trying it against all the open edges, and I was able to speed things up a little bit by going through all pieces in a tray and then rotating the tray 180 degrees rather than individually rotating the pieces, but ultimately any time I'm brute forcing something I feel like I must be doing something wrong.

Are there any strategies or tips to do better than brute force, here?

Some sample images as requested of what I was considering to be a "wide piece":

and a "thin flange":

and some general pieces to show if the pegs have any obvious categories:

• I can see if I can get some pictures this evening; to try to describe what I mean, a "thin flange" would mean a hole-side of a piece where the hole is significantly towards one side or the other, rather than being more or less centered. A "wide" piece would be....for some reason I consider "pegs on the top and bottom, holes on the left and right" to be the "natural" orientation of a piece, so a "wide" piece is one where the distance between the sides-with-holes is noticable larger than the distance between the sides-with-pegs. Jun 8 at 19:53
• Well, they certainly vary enough that it works as a jigsaw puzzle, e.g. it's rare that I can't tell if a piece's fit is correct or not when I'm trying to set a piece into place. I haven't been able to see any obvious peg classification like "these pegs are triangular, these are square-ish, these are round", though. Jun 8 at 20:39
• My first strategy would be to spot the most recognisable/extreme shape at unfinished edges of the puzzle itself, such as the thinnest spike, or tightest angle. A corner location is best, because you have the most clues. Not the other way round (trying to fit each piece) because it can only fit where it touches an edge, so you'll be conducting fruitless searches with those that "don't go" yet. Jun 9 at 6:50
• Where are the edge pieces?
– Moti
Jun 12 at 0:16
• The puzzle is maybe 80% complete, the edge pieces are all already placed; the pictures were just to give some samples of what's remaining. Jun 13 at 1:56