I have the following code, what I want is that the two buttons of each column in the second row occupy 100% of the space of the .col class as it happens in the first row with the btn-block class, how could I do it?
*{
border-radius: 0px !important;
}
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0-beta/css/bootstrap.min.css">
<script src="https://code.jquery.com/jquery-3.2.1.slim.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.11.0/umd/popper.min.js"></script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0-beta/js/bootstrap.min.js"></script>
<div class="container-fluid">
<div class="row">
<div class="col">
<button type="button" class="btn btn-block btn-dark">Column 1 - Row 1</button>
</div>
<div class="col">
<button type="button" class="btn btn-block btn-dark">Column 2 - Row 1</button>
</div>
</div>
<br />
<div class="row">
<div class="col">
<div class="btn-group btn-group-block" role="group">
<button type="button" class="btn btn-secondary">356a</button>
<button type="button" class="btn btn-danger">Column 1 - Row 2</button>
</div>
</div>
<div class="col">
<div class="btn-group" role="group">
<button type="button" class="btn btn-secondary">356a</button>
<button type="button" class="btn btn-danger">Column 2 - Row 2</button>
</div>
</div>
</div>
</div>
The solution to layout themes is more than CSS, you can add some classes and control the width of the rows. For example: