Which value is used to evenly space rows of flex items vertically within a container with no space above the first or below the last elements?

The value used to evenly space rows of flex items vertically within a container with no space above the first or below the last elements is space-between in CSS.

Here's a step-by-step guide on how to use it:

1. First, you need to set the container to display as a flex container. You can do this by setting the display property to flex or inline-flex. For example:

.container {
  display: flex;
}

2. Next, you need to set the direction of the flex items. If you want the items to be in rows, you can set the flex-direction property to row. For example:

.container {
  display: flex;
  flex-direction: row;
}

3. Then, to evenly space the flex items vertically with no space above the first or below the last elements, you can set the justify-content property to space-between. For example:

.container {
  display: flex;
  flex-direction: row;
  justify-content: space-between;
}

This will ensure that the flex items are evenly spaced vertically within the container, with no space above the first item or below the last item.