Tiered link building uses two levels of links to boost your site’s ranking....

https://www.4shared.com/office/BIObF2h6fa/pdf-72309-44204.html

Tiered link building uses two levels of links to boost your site’s ranking. Tier 1 links point directly to your site and carry real weight. Tier 2 links support those Tier 1 links, making them stronger and more effective