Different types of knowledge have been found important for a successful search. We designed a user interface: CIRR tool (Collaborative Information Retrieval Research) that supports sharing of search results as well as search queries (knowledge of finding the relevant items). We conducted a pilot study to explore what factors would affect the use of these knowledge sharing features. The results demonstrate that knowledge sharing in general is preferred by only some subjects for some tasks. For those who preferred sharing they share search queries, domain knowledge, and search results, rather than the usefulness judgment. The findings also show that knowledge sharing does not seem to have effects on search performance. However, it is significantly associated with the perceived task difficulty. The possible reasons leading to these results are analyzed. Limitations of this study are pointed out and the future studies are discussed.