CSS的background

 .block{
   width: 200px;
   height: 200px;
   padding: 25px;
   background-image:linear-gradient(#58a,#58a)
     ,linear-gradient(to left,#0292f3 33.3%,transparent 0,transparent 66.6%  , #0292f3 0)
     ,linear-gradient(#0292f3 33.3%,transparent 0,transparent 66.6%  , #0292f3 0)
     ,linear-gradient(to right,#0292f3 33.3%,transparent 0,transparent 66.6%  , #0292f3 0)
     ,linear-gradient(to bottom,#0292f3 33.3%,transparent 0,transparent 66.6%  , #0292f3 0);
      background-clip: content-box,border-box,border-box,border-box,border-box;
     background-position: 0 0,0 0,100% 0,0 100%,0;
     background-size: 100%,100% 5px,5px 100%,100% 5px,5px 100%;
     background-repeat: repeat,no-repeat,no-repeat,no-repeat,no-repeat;
 }