Platelet RAP1 signaling is critical for hemostasis at sites of injury. Determination of hemostasis using tail clip (A-B) or saphenous vein laser injury (C-D) model in control (Rap1a^fl/flRap1b^fl/flPf4-Cre⁻; black bars; black line), Rap1a^fl/flRap1b^+/flPf4-Cre⁺ (green bars; green line), Rap1a^+/flRap1b^fl/flPf4-Cre⁺ (orange bars; orange line), and Rap1a/b-mKO (Rap1a^fl/flRap1b^fl/flPf4-Cre⁺; red bars; red line) mice. Tail bleeding time (A) and blood loss volume (B) were determined following tail clipping. (C) Repeated laser injuries were made to the saphenous vein using an Ablate! photoablation system equipped with an attenuable 532-nm pulse laser (Intelligent Imaging Innovations, Denver, CO). Bleeding time was assessed as time (seconds) to stable hemostatic plug formation (no leakage of blood for >60 seconds) within the laser injury–induced vascular lesion. Talin1-mKO mice (Talin1^fl/flPf4-Cre⁺; blue bar), which bleed for the entire observation period, are shown for comparison. (D) Platelet accumulation was recorded using a Zeiss Axio Examiner Z1 microscope (Intelligent Imaging Innovations) equipped with a 20×/1 numerical aperture water immersion objective lens and determined as sum fluorescence intensity (SFI) of GPIX-labeled platelets ± SEM at the site of injury over time; data were analyzed using SlideBook 5.0 software (Intelligent Imaging Innovations). *P < .05, **P < .01, ***P < .001. ns, not significant.