Obstruction defines the U.S. Senate for both casual observers and scholars alike, with filibusters among the most well known parliamentary tactics in the world. This emphasis on public filibusters masks how obstruction shapes legislation, however. Filibusters are the end of a long process of obstruction and management rather than a stand-alone tactic by senators. While scholars have passingly mentioned off-floor tactics, the connections between these procedural tools for obstruction by senators and management by leaders has yet to be explored. This dissertation provides the first analysis of bill-level obstruction throughout the U.S. Senate, using both on- and off-floor procedural tools. I focus on how holds, Unanimous Consent Agreements, and filibusters are used, when these tactics can be expected, and how they affect passage. I also ask how these tools are connected, seeking to understand how the private actions by members and leaders shape obstruction the public sees. I find clear patterns for when these tactics are used, that holds and Unanimous Consent Agreements clearly relate to passage, and holds are powerful predictors of filibusters. This dissertation explores the broader system of obstruction in the U.S. Senate, shedding light on how obstruction actually works.