We aim to improve the quality of time spent in co-located social interactions by encouraging people to limit their smartphone usage together. We present a prototype called Lock n' LoL, an app that allows co-located users to lock their smartphones and limit their usage by enforcing users to ask for explicit use permission. From our preliminary study, we designed two modes to deal with the dynamics of smartphone use during the co-located social interactions: (1) socializing mode (i.e., locking smartphones to limit usage together) and (2) temporary use mode (i.e., requesting/granting temporary smartphone use). We conducted a pilot study (n = 20) with our working prototype, and the results documented the helpfulness of Lock n' LoL when used in socializing.