need help in simulink, about half wave rectifier, drawing box, noise generator

hi dear all i have to do a simulink program, but i have some question:

1.in the image, how can i implant the half wave rectifier in simulink? 2. how can i draw a box around model part? (its answered in mathnews by Guy Rouleau, but didnt work for me, cause i have Sum block)

http://postimg.org/image/r8uimrxin/