user80905: Let's use block #100205
https://www.blockchain.com/en/btc/block/0000000000033d0de6f4ebe93b3b142424cdbecf4bd98b948e856c4a55f09f76
This block contains 6 transactions. After the second level of hashing you end up with 3 nodes. What is the fix for this? Do you create two 5's and 6's?

user7272: You would duplicate the hash of the last two txs. The tree would "look" something like this:
             abcdefef
              /  \            
           /        \          
        /              \       
      abcd             efef     
      /  \            /  \    
   /        \      /        \  
  ab        cd    ef        ef 
 / \        / \   / \  
a   b      c  d  e   f 


80905: <p>Let's use block #100205
<a href="https://www.blockchain.com/en/btc/block/0000000000033d0de6f4ebe93b3b142424cdbecf4bd98b948e856c4a55f09f76" rel="nofollow noreferrer">https://www.blockchain.com/en/btc/block/0000000000033d0de6f4ebe93b3b142424cdbecf4bd98b948e856c4a55f09f76</a></p>

<p>This block contains 6 transactions. After the second level of hashing you end up with 3 nodes. What is the fix for this? Do you create two 5's and 6's?</p>
 7272: <p>You would duplicate the hash of the last two txs. The tree would "look" something like this:</p>

<pre><code>             abcdefef
              /  \            
           /        \          
        /              \       
      abcd             efef     
      /  \            /  \    
   /        \      /        \  
  ab        cd    ef        ef 
 / \        / \   / \  
a   b      c  d  e   f 
</code></pre>
