Display collections of records in groups using Ruby's Enumerable's each_slice method.

enumerable_each_slice.html.erb

# So you have a collection of records you want to display in rows of 3.

# Use Enumerable's each_slice method:

<%= content_tag :div, :class => :thumbs do %>
	<% @thumbs.each_slice(3) do |slice| %>
		<%= content_tag :div, :class => :thumbs_row do %>
			<% slice.each do |thumb| %>
				<%= render 'thumb' %>
			<% end %>
		<% end %>
	<% end %>
<% end %>

# Output:

<div class="thumbs">
	<div class="thumbs_row">
		<div class="thumb"><img src="thumb_1.jpg" /></div>
		<div class="thumb"><img src="thumb_2.jpg" /></div>
		<div class="thumb"><img src="thumb_3.jpg" /></div>
	</div>
	<div class="thumbs_row">
		<div class="thumb"><img src="thumb_4.jpg" /></div>
		<div class="thumb"><img src="thumb_5.jpg" /></div>
		<div class="thumb"><img src="thumb_6.jpg" /></div>
	</div>
	<div class="thumbs_row">
		<div class="thumb"><img src="thumb_7.jpg" /></div>
		<div class="thumb"><img src="thumb_8.jpg" /></div>
		<div class="thumb"><img src="thumb_9.jpg" /></div>
	</div>
</div>