Laboratory instruction is critical to the understanding of biology and is a central piece of biological sciences instruction. Although much investigation has focused on the content of biology laboratory exercises, we contend that understanding the extent to which the laboratory materials can aid or limit experimental investigation is of equal importance. In this study, therefore, we investigate the role of timing and availability of laboratory equipment in the context of two different laboratory exercises. We use both case study and an experimental approach to investigate how laboratory materials guide the planning, context, creativity, and timing of ideas shared among students. Our data support the notion that providing students with laboratory equipment before students plan and consider different experimental approaches can constrain students' ideas and encourage tool-focused solutions to experimental design tasks. (Contains 2 tables.)