Snyder Notation Practice
Exercises to Build Your Skills
Reading about Snyder Notation is one thing — applying it is another. This page provides guided exercises to help you internalize the technique. Work through these examples, then practice on real puzzles.
- Exercise 1: Identify bi-value situations
- Exercise 2: Find what to mark
- Exercise 3: Spot the patterns
- Exercise 4: Full box analysis
- Practice: Apply to real puzzles
Warm-Up: Know the Rule
Before diving into exercises, make sure you understand the core rule: mark a candidate only when it can appear in exactly 2 cells within a box.
Ready? Let's practice applying this rule.
Exercise 1: Count the Options
For each scenario, count how many cells the given number can go in within the box. Then decide: should you mark it?
Scenario A
A 3×3 box has these numbers filled: 1, 3, 5, 7, 9
Question: How many cells can 2 go in?
Show Answer
4 cells are empty (9 - 5 = 4). You'd need to check row/column constraints to narrow further, but with 4 empty cells, 2 likely has 2-4 options.
⚠️ If 3+ options remain after checking constraints → Don't mark
Scenario B
A 3×3 box has 7 numbers filled. Only 2 cells are empty.
One empty cell's row already contains 4.
Question: Should you mark 4?
Show Answer
With only 2 empty cells, and one eliminated by the row constraint,4 can only go in 1 cell.
🎯 Don't mark — PLACE IT! This is a hidden single.
Scenario C
A box has 6 numbers filled. 3 cells are empty.
After checking rows and columns, 8 is eliminated from one cell.
Question: Should you mark 8?
Show Answer
3 empty cells - 1 eliminated = 2 possible cells for 8.
✅ Yes, mark it! Write a small 8 in the corners of both cells.
Exercise 2: Find the Marks
Given this box state, determine which numbers should be marked using Snyder Notation:
The Box
Given: 5, 3, 9, 1, 7 are placed. Empty cells: R1C2, R2C1, R3C1, R3C3
Additional constraints:
- Row 1 already contains: 2, 4
- Row 2 already contains: 6, 8
- Row 3 already contains: none of the missing numbers
- Column 1 already contains: 4
- Column 2 already contains: 2, 6
- Column 3 already contains: 8
Question: Which numbers should get Snyder marks, and in which cells?
Show Solution
Missing from box: 2, 4, 6, 8
R1C2 ❌ (row has 2), others need column check
→ If exactly 2 cells remain, mark them
→ Only R3C1 and R3C3 possible = 2 cells → MARK!
→ Only R3C1 and R3C3 possible = 2 cells → MARK!
→ Only R1C2 and R3C1 possible = 2 cells → MARK!
Exercise 3: Spot the Pattern
You've applied Snyder marks. Now identify what pattern is revealed:
The Marks
In a box, you've marked:
- 3 is marked in R4C1 and R4C3 (same row)
- 7 is marked in R5C2 and R6C2 (same column)
Question: What patterns can you use?
Show Answer
Both marks for 3 are in Row 4. This means 3 must be in one of these cells. Therefore, eliminate 3 from all other cells in Row 4 (outside this box).
Both marks for 7 are in Column 2. Therefore, eliminate 7 from all other cells in Column 2 (outside this box).
Exercise 4: Full Box Analysis
Analyze an entire box systematically. Check each number 1-9 and determine the Snyder marks:
Box Setup
In box: 2, 4, 6, 8 | Missing: 1, 3, 5, 7, 9
Empty cells: R1C1, R1C3, R2C2, R3C1, R3C2
(Assume no external row/column constraints for this exercise — focus on the box only)
Task: Work through each missing number. Which get Snyder marks?
Show Analysis
With 5 empty cells and no external constraints:
Exercise 5: Update After Placement
Snyder marks must be updated when you place a number. Practice this critical skill:
Scenario
You have these existing Snyder marks in a box:
- 5 marked in R1C1 and R1C3
- 9 marked in R2C1 and R3C1
You now place 5 in R1C1 (maybe from a row constraint elsewhere).
Question: What updates are needed?
Show Answer
5 is now placed. Remove the Snyder mark for 5 from R1C3 — it's no longer a candidate anywhere.
9 was marked in R2C1 and R3C1. Placing 5 in R1C1 doesn't affect these — 9 still has exactly 2 options. Keep these marks.
With R1C1 filled, some numbers that had 3 options might now have 2. Rescan the box to find new Snyder opportunities.
Self-Test Questions
Quick-fire questions to test your understanding:
Q1: You find that 7 can go in 3 cells within a box. Do you mark it?
Answer
❌ No. Only mark when exactly 2 cells are possible.
Q2: Both of your Snyder marks for 4 are in Row 6. What can you conclude?
Answer
This is a pointing pair. Eliminate 4 from all other cells in Row 6 (outside this box).
Q3: After placing a number, one of your Snyder pairs now has only one cell marked. What do you do?
Answer
🎯 Place that number! It's now a hidden single — the only remaining option.
Q4: Where should you write Snyder marks in a cell?
Answer
In the corners. This distinguishes them from full notation (center) and leaves room for the final answer.
Q5: Which boxes should you focus on first when applying Snyder Notation?
Answer
Boxes with the most givens (5-7 filled). They're most likely to have useful bi-value situations.
Practice on Real Puzzles
The best way to internalize Snyder Notation is to use it on actual puzzles. Here's a structured practice plan:
7-Day Snyder Practice Plan
Start Practicing Now
Apply what you've learned on our free puzzles. Corner marks are perfect for Snyder Notation.
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