The design requirements of fuel transport flasks for containment integrity is well covered by international regulations. Less well defined are the requirements for restraint, or tiedown, as a means of securing the transport flask to its prime mover. This paper refers specifically to the NTL range of LWR fuel flasks, though many principles are applicable to a wider range of transport packages. The tiedown system is defined, and different aspects discussed in detail: the practical requirements, for example, where operation, maintenance and inspection are considered, and the need for the tiedown to harmonise with the flask so that performance is not impaired. A review of regulations and guidelines appropriate to tiedowns is included, together with a statement on their applicability. The derivation of the standards applied by NTL is described, in the context of transport by rail, sea and road. Aspects of detail design of various components of the tiedown system are described, with specific reference to the influence of this design on package performance. NTL has conducted a number of practical trials to evaluate typical values of accelerations encountered by flasks and their tiedown systems in the various transport modes. Results of these practical trials are available as input to future designs. In conclusion, the paper serves to highlight the high degree of care and consideration paid to this peripheral area of irradiated fuel transport.