to the invention fig2 is a top view of the apparatus 10 of fig1 fig3 is a side view of the apparatus of fig1 the sleeving apparatus 10 includes three modules a tray inserter module 20 for receiving loaded trays and inserting the trays in a sleeve a sleeve supply module 60 for holding sleeve blanks ready for transfer to the inserter module and a sleeve preparation module 64 that obtains sleeve blanks from the supply module 60 forms the blanks into open sleeves and positions the blanks at the inserter module for insertion of a tray the tray inserter module 20 includes a conveyor 22 comprising a suitable roller conveyor for moving a tray to the tray inserter module from an upstream mail sorting station not illustrated as is known in the material handling art a tray of mail is first received by the conveyor 22 at position a tray position sensing means 23 senses the tray at position a and at various positions in the tray inserter module 20 signals from the tray sensing means 23 are used to initiate and control various operations as further described below in a preferred embodiment the tray sensing means 23 comprises a plurality of photocell devices suitably positioned and integrated to monitor the various tray positions in the inserter module 20 a roller brake 25 halts forward movement of the tray at position a the roller brake 25 comprises a pneumatically actuated cylinder having a friction surface that moves upward to stop the rollers in the conveyor 22 path to hold the tray in the position a.