Rikonardo

div{
  -webkit-clip-path: polygon(0 10%, 100% 0, 100% 90%, 0 100%);
          clip-path: polygon(0 10%, 100% 0, 100% 90%, 0 100%);
}

<div class="main">
    <div class="1and3">
        <div class="block1">
        BLOCK1
        </div>
        <div class="block3">
        BLOCK3
        </div>
    </div>
    <div class="block2">
    BLOCK2
    </div>
</div>