When you see an L pattern you will often be able to find twins and/or triplets using it. You will also find where other numbers go even if you can't solve the twins and triplets you find. Just knowing about them can help you.

Details

The L pattern exists when there is a wall that has one populated cell adjacent to it. The wall and the adjacent cell must be in the same box. There are two L patterns, one in box 1 and one in box 3, in the figure below.

Figure 1
NOTE: this puzzle is not valid - it is only used to illustrate the L pattern

Let's see how much information we can get from this example. Look at figure 1. The 1524 in box 1 is an L pattern. The 1347 in box 3 is also an L pattern -- the 3 can be in any cell in box 3 column 8.

Let's look at box 1 first. Notice that there is a 6 and a 7 in box 7 that can only go in column 2 in box 1. The L pattern helped identify those 67 twins in box 1. The twins can't be solved yet. But that also helps us find triplets in box 1 column 3. The triplets in column 3 are 3, 8 and 9. Although we can't solve them, because of the L pattern we were able to identify in which column every number goes in box 1.

Now look at boxes 4 and 7. The twins and triplets in box 1 will help us find numbers in these boxes too.

Figure 2
NOTE: this puzzle is not valid - it is only used to illustrate the L pattern

Figure 2 shows all of the numbers found because there is an L pattern in box 1 (red numbers). Make sure you understand how each of these numbers were solved.

Extra Credit!

It was mentioned above that box 3 also has an L pattern. As an exercise see how many numbers you can find by looking at the L pattern in that box.

Video about the L pattern
Watch this video for more info and examples of the L pattern

See more videos illustrating the L pattern in the video index -- videos 58, 75 and 81.