Skyscraper: compare two offset strong links
A Skyscraper uses two parallel strong links for one digit. One end of each link aligns to form the base; the other two ends form the roofs.
Key idea
At least one roof must be true, so any candidate that sees both roofs is impossible.
See the move, step by step
Follow candidate 7 through columns 1 and 6.
Step 1 of 4
Find two parallel strong links
Columns 1 and 6 each contain exactly two relevant 7 candidates.
Step 2 of 4
Identify the base and roofs
R3C1 and R3C6 form the aligned base. R1C1 and R2C6 are the two roof cells.
Step 3 of 4
Use both roofs
R1C4 sees R1C1 along row 1 and R2C6 inside box 2. It therefore cannot be 7.
Step 4 of 4
Preserve the chain
The roof values remain unknown, but one is guaranteed true and the shared peer stays eliminated.
Try it on today's puzzle
Search rows or columns with exactly two candidates for one digit. One pair of endpoints must align while the roofs remain offset.
Play today