Printed in PLA on my UM2 with "normal quality" settings, standing vertically without support, raft or brim. I use a 60° heated glass plate primed with 3Dlac for the build surface and it works fine even without a brim. The sticking surface is very thin vertically, but allows for large multiprints. Printed on the UM2 it exactly fits the t-rail of the clamp. The friction fit is enough not to come off accidentally. I included another design that uses a spring-like mechanism for increased friction on the clamp, you may try this on other printers if the normal version fits too loose. You want to use PLA for this, because it is resistive to most solvents that may be in glue or paint that you use on the clamped pieces.