https://codepen.io/hana78786/full/LYdagzQ
<link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.3.1/css/bootstrap.min.css" integrity="sha384-ggOyR0iXCbMQv3Xipma34MD+dH/1fQ784/j6cY/iJTQUOhcWr7x9JvoRxT2MZw1T" crossorigin="anonymous">
<style>
div{
border: 1px solid red;
}
</style>
</head>
<body>
<h1>그리드시스템</h1>
<div class = "row">
<div class="col-md-1">md-1</div>
<div class="col-md-1">md-1</div>
<div class="col-md-1">md-1</div>
<div class="col-md-1">md-1</div>
<div class="col-md-1">md-1</div>
<div class="col-md-1">md-1</div>
<div class="col-md-1">md-1</div>
<div class="col-md-1">md-1</div>
<div class="col-md-1">md-1</div>
<div class="col-md-1">md-1</div>
<div class="col-md-1">md-1</div>
<div class="col-md-1">md-1</div>
</div>
<br><br><br><br><br>
<div class="row">
<div class="col-md-2">md-2</div>
<div class="col-md-2">md-2</div>
<div class="col-md-2">md-2</div>
<div class="col-md-2">md-2</div>
<div class="col-md-2">md-2</div>
<div class="col-md-2">md-2</div>
</div>
<br><br><br><br><br>
<div class="row">
<div class="col-md-3">md-3</div>
<div class="col-md-3">md-3</div>
<div class="col-md-3">md-3</div>
<div class="col-md-3">md-3</div>
</div>
<br><br><br><br><br>
<div class="row">
<div class="col-md-4">md-4</div>
<div class="col-md-8">md-8</div>
</div>
<div class="container">
<div class="row header">
<div class ="col-12 col-md-4 col-sm-4">logo</div>
<div class ="col-12 col-md-4 col-sm-8">search</div>
<div class ="d-none col-md-4 d-md-block">reserved</div>
</div>
<div class="row body">
<div class = "col-md-4 col-sm-12">login</div>
<div class = "col-md-8 col-sm-12">main</div>
</div>
<div class="row footer">
<div class="col-md-6 col-sm-3">license</div>
<div class="col-md-6 col-sm-9">company info</div>
</div>
</div>