Protege-TS is a software tool developed to support and partially automate the process of constructing OWL ontology signatures. It works from an OWL 2 based source ontology to assist the user in creating a signature which is composed of a list of concepts and roles. Such signature lists are often needed when working with ontologies. For example, the signature can be fed to a forgetting or modularisation tool in order to compute an output ontology which retains all the relevant logical entailments of the source ontology. The Protege-TS tool implements a range of operations which allow the user to create and edit signatures of concept and role names in ontologies. The functionality and architecture of the tool which has been implemented as a Java plugin to Protege, and an evaluation of the tool when applied to several large scale ontologies, with an example focus on the medical ontology SNOMED-CT is described in this paper.