This article analyses anthropometric forms used in three different Dutch contexts around 1900: an expedition in Dutch New Guinea, the Dutch police and prison registration system, where ‘Bertillonage’ was used to identify recidivist criminals, and a state-owned reform school for girls. The authors identify the loose form as an innovative ‘paper technology’ within anthropometry that opened up entirely new ways of linking bodies to identities and was critically important in inscribing bodies into knowledge systems. The article demonstrates how this crucial innovation within anthropometry took shape in practice. In order to show the techniques through which the inscription of bodies into knowledge systems took place, the article demonstrates how the forms organized, standardized and directed measuring practices and prepared the data for further use in filing systems. Moreover, it draws attention to the tension between the forms’ potential and actual practices. The article concludes by considering the ways these forms were filed and used as ‘data’ by judicial authorities, child protection professionals and racial and criminological scientists, each of whom produced different forms of ‘paper identity’ and whose anthropometric practices enacted different bodies.