At first look, Stumbling Blocks looks very much like Road Blocks; physically they are about the same dimensions at 4" square and consist of a box tray with wide edges and four pieces to be inserted into the centre square hole of the tray as the objective. As you can see from the photo, there are channels constructed inside the box so its not a simple matter of trying to fit the pieces in like the typical packing puzzle. The box is Maple and the pieces Jatoba. Made by Tom Lensch, my copy has excellent build quality, fit and finish. All the pieces fit snugly and nicely. And there is no need to use any force for this puzzle.
For those who have solved the Road Blocks, you may think you have some clue as to how to solve Stumbling Blocks; well possibly. However, the solutions for both puzzles are totally different and Stumbling Blocks has IMHO a tad more elegant solution. A solution I might add that is quite characteristic of Goh's design style. Those of you acquainted with Goh many puzzle designs, especially the packing ones will know what I mean. Perhaps because I have played with a number of Goh's puzzles and familiar with his style (and tricks) that I didn't find Stumbling Blocks too difficult. But this is not to say that Stumbling Blocks is easy as I saw quite a few IPP attendees pouring themselves over the puzzle at the judging table without much success.
If you are interested in a nice well made packing style puzzle with just 4 pieces, topped off with a more than moderately difficult challenge and a unique (unusual) solution, Stumbling Blocks may just be the puzzle for you. For serious collectors, a definite must-have!
Both Stumbling Blocks and Chain Store are available from Tom Lensch.